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References in Research – Types, Examples and Writing Guide

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References in Research

Definition:

References in research are a list of sources that a researcher has consulted or cited while conducting their study. They are an essential component of any academic work, including research papers, theses, dissertations, and other scholarly publications.

Types of References

There are several types of references used in research, and the type of reference depends on the source of information being cited. The most common types of references include:

References to books typically include the author’s name, title of the book, publisher, publication date, and place of publication.

Example: Smith, J. (2018). The Art of Writing. Penguin Books.

Journal Articles

References to journal articles usually include the author’s name, title of the article, name of the journal, volume and issue number, page numbers, and publication date.

Example: Johnson, T. (2021). The Impact of Social Media on Mental Health. Journal of Psychology, 32(4), 87-94.

Web sources

References to web sources should include the author or organization responsible for the content, the title of the page, the URL, and the date accessed.

Example: World Health Organization. (2020). Coronavirus disease (COVID-19) advice for the public. Retrieved from https://www.who.int/emergencies/disease/novel-coronavirus-2019/advice-for-public

Conference Proceedings

References to conference proceedings should include the author’s name, title of the paper, name of the conference, location of the conference, date of the conference, and page numbers.

Example: Chen, S., & Li, J. (2019). The Future of AI in Education. Proceedings of the International Conference on Educational Technology, Beijing, China, July 15-17, pp. 67-78.

References to reports typically include the author or organization responsible for the report, title of the report, publication date, and publisher.

Example: United Nations. (2020). The Sustainable Development Goals Report. United Nations.

Formats of References

Some common Formates of References with their examples are as follows:

APA (American Psychological Association) Style

The APA (American Psychological Association) Style has specific guidelines for formatting references used in academic papers, articles, and books. Here are the different reference formats in APA style with examples:

Author, A. A. (Year of publication). Title of book. Publisher.

Example : Smith, J. K. (2005). The psychology of social interaction. Wiley-Blackwell.

Journal Article

Author, A. A., Author, B. B., & Author, C. C. (Year of publication). Title of article. Title of Journal, volume number(issue number), page numbers.

Example : Brown, L. M., Keating, J. G., & Jones, S. M. (2012). The role of social support in coping with stress among African American adolescents. Journal of Research on Adolescence, 22(1), 218-233.

Author, A. A. (Year of publication or last update). Title of page. Website name. URL.

Example : Centers for Disease Control and Prevention. (2020, December 11). COVID-19: How to protect yourself and others. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html

Magazine article

Author, A. A. (Year, Month Day of publication). Title of article. Title of Magazine, volume number(issue number), page numbers.

Example : Smith, M. (2019, March 11). The power of positive thinking. Psychology Today, 52(3), 60-65.

Newspaper article:

Author, A. A. (Year, Month Day of publication). Title of article. Title of Newspaper, page numbers.

Example: Johnson, B. (2021, February 15). New study shows benefits of exercise on mental health. The New York Times, A8.

Edited book

Editor, E. E. (Ed.). (Year of publication). Title of book. Publisher.

Example : Thompson, J. P. (Ed.). (2014). Social work in the 21st century. Sage Publications.

Chapter in an edited book:

Author, A. A. (Year of publication). Title of chapter. In E. E. Editor (Ed.), Title of book (pp. page numbers). Publisher.

Example : Johnson, K. S. (2018). The future of social work: Challenges and opportunities. In J. P. Thompson (Ed.), Social work in the 21st century (pp. 105-118). Sage Publications.

MLA (Modern Language Association) Style

The MLA (Modern Language Association) Style is a widely used style for writing academic papers and essays in the humanities. Here are the different reference formats in MLA style:

Author’s Last name, First name. Title of Book. Publisher, Publication year.

Example : Smith, John. The Psychology of Social Interaction. Wiley-Blackwell, 2005.

Journal article

Author’s Last name, First name. “Title of Article.” Title of Journal, volume number, issue number, Publication year, page numbers.

Example : Brown, Laura M., et al. “The Role of Social Support in Coping with Stress among African American Adolescents.” Journal of Research on Adolescence, vol. 22, no. 1, 2012, pp. 218-233.

Author’s Last name, First name. “Title of Webpage.” Website Name, Publication date, URL.

Example : Centers for Disease Control and Prevention. “COVID-19: How to Protect Yourself and Others.” CDC, 11 Dec. 2020, https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html.

Author’s Last name, First name. “Title of Article.” Title of Magazine, Publication date, page numbers.

Example : Smith, Mary. “The Power of Positive Thinking.” Psychology Today, Mar. 2019, pp. 60-65.

Newspaper article

Author’s Last name, First name. “Title of Article.” Title of Newspaper, Publication date, page numbers.

Example : Johnson, Bob. “New Study Shows Benefits of Exercise on Mental Health.” The New York Times, 15 Feb. 2021, p. A8.

Editor’s Last name, First name, editor. Title of Book. Publisher, Publication year.

Example : Thompson, John P., editor. Social Work in the 21st Century. Sage Publications, 2014.

Chapter in an edited book

Author’s Last name, First name. “Title of Chapter.” Title of Book, edited by Editor’s First Name Last name, Publisher, Publication year, page numbers.

Example : Johnson, Karen S. “The Future of Social Work: Challenges and Opportunities.” Social Work in the 21st Century, edited by John P. Thompson, Sage Publications, 2014, pp. 105-118.

Chicago Manual of Style

The Chicago Manual of Style is a widely used style for writing academic papers, dissertations, and books in the humanities and social sciences. Here are the different reference formats in Chicago style:

Example : Smith, John K. The Psychology of Social Interaction. Wiley-Blackwell, 2005.

Author’s Last name, First name. “Title of Article.” Title of Journal volume number, no. issue number (Publication year): page numbers.

Example : Brown, Laura M., John G. Keating, and Sarah M. Jones. “The Role of Social Support in Coping with Stress among African American Adolescents.” Journal of Research on Adolescence 22, no. 1 (2012): 218-233.

Author’s Last name, First name. “Title of Webpage.” Website Name. Publication date. URL.

Example : Centers for Disease Control and Prevention. “COVID-19: How to Protect Yourself and Others.” CDC. December 11, 2020. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html.

Author’s Last name, First name. “Title of Article.” Title of Magazine, Publication date.

Example : Smith, Mary. “The Power of Positive Thinking.” Psychology Today, March 2019.

Author’s Last name, First name. “Title of Article.” Title of Newspaper, Publication date.

Example : Johnson, Bob. “New Study Shows Benefits of Exercise on Mental Health.” The New York Times, February 15, 2021.

Example : Thompson, John P., ed. Social Work in the 21st Century. Sage Publications, 2014.

Author’s Last name, First name. “Title of Chapter.” In Title of Book, edited by Editor’s First Name Last Name, page numbers. Publisher, Publication year.

Example : Johnson, Karen S. “The Future of Social Work: Challenges and Opportunities.” In Social Work in the 21st Century, edited by John P. Thompson, 105-118. Sage Publications, 2014.

Harvard Style

The Harvard Style, also known as the Author-Date System, is a widely used style for writing academic papers and essays in the social sciences. Here are the different reference formats in Harvard Style:

Author’s Last name, First name. Year of publication. Title of Book. Place of publication: Publisher.

Example : Smith, John. 2005. The Psychology of Social Interaction. Oxford: Wiley-Blackwell.

Author’s Last name, First name. Year of publication. “Title of Article.” Title of Journal volume number (issue number): page numbers.

Example: Brown, Laura M., John G. Keating, and Sarah M. Jones. 2012. “The Role of Social Support in Coping with Stress among African American Adolescents.” Journal of Research on Adolescence 22 (1): 218-233.

Author’s Last name, First name. Year of publication. “Title of Webpage.” Website Name. URL. Accessed date.

Example : Centers for Disease Control and Prevention. 2020. “COVID-19: How to Protect Yourself and Others.” CDC. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html. Accessed April 1, 2023.

Author’s Last name, First name. Year of publication. “Title of Article.” Title of Magazine, month and date of publication.

Example : Smith, Mary. 2019. “The Power of Positive Thinking.” Psychology Today, March 2019.

Author’s Last name, First name. Year of publication. “Title of Article.” Title of Newspaper, month and date of publication.

Example : Johnson, Bob. 2021. “New Study Shows Benefits of Exercise on Mental Health.” The New York Times, February 15, 2021.

Editor’s Last name, First name, ed. Year of publication. Title of Book. Place of publication: Publisher.

Example : Thompson, John P., ed. 2014. Social Work in the 21st Century. Thousand Oaks, CA: Sage Publications.

Author’s Last name, First name. Year of publication. “Title of Chapter.” In Title of Book, edited by Editor’s First Name Last Name, page numbers. Place of publication: Publisher.

Example : Johnson, Karen S. 2014. “The Future of Social Work: Challenges and Opportunities.” In Social Work in the 21st Century, edited by John P. Thompson, 105-118. Thousand Oaks, CA: Sage Publications.

Vancouver Style

The Vancouver Style, also known as the Uniform Requirements for Manuscripts Submitted to Biomedical Journals, is a widely used style for writing academic papers in the biomedical sciences. Here are the different reference formats in Vancouver Style:

Author’s Last name, First name. Title of Book. Edition number. Place of publication: Publisher; Year of publication.

Example : Smith, John K. The Psychology of Social Interaction. 2nd ed. Oxford: Wiley-Blackwell; 2005.

Author’s Last name, First name. Title of Article. Abbreviated Journal Title. Year of publication; volume number(issue number):page numbers.

Example : Brown LM, Keating JG, Jones SM. The Role of Social Support in Coping with Stress among African American Adolescents. J Res Adolesc. 2012;22(1):218-233.

Author’s Last name, First name. Title of Webpage. Website Name [Internet]. Publication date. [cited date]. Available from: URL.

Example : Centers for Disease Control and Prevention. COVID-19: How to Protect Yourself and Others [Internet]. 2020 Dec 11. [cited 2023 Apr 1]. Available from: https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html.

Author’s Last name, First name. Title of Article. Title of Magazine. Year of publication; month and day of publication:page numbers.

Example : Smith M. The Power of Positive Thinking. Psychology Today. 2019 Mar 1:32-35.

Author’s Last name, First name. Title of Article. Title of Newspaper. Year of publication; month and day of publication:page numbers.

Example : Johnson B. New Study Shows Benefits of Exercise on Mental Health. The New York Times. 2021 Feb 15:A4.

Editor’s Last name, First name, editor. Title of Book. Edition number. Place of publication: Publisher; Year of publication.

Example: Thompson JP, editor. Social Work in the 21st Century. 1st ed. Thousand Oaks, CA: Sage Publications; 2014.

Author’s Last name, First name. Title of Chapter. In: Editor’s Last name, First name, editor. Title of Book. Edition number. Place of publication: Publisher; Year of publication. page numbers.

Example : Johnson KS. The Future of Social Work: Challenges and Opportunities. In: Thompson JP, editor. Social Work in the 21st Century. 1st ed. Thousand Oaks, CA: Sage Publications; 2014. p. 105-118.

Turabian Style

Turabian style is a variation of the Chicago style used in academic writing, particularly in the fields of history and humanities. Here are the different reference formats in Turabian style:

Author’s Last name, First name. Title of Book. Place of publication: Publisher, Year of publication.

Example : Smith, John K. The Psychology of Social Interaction. Oxford: Wiley-Blackwell, 2005.

Author’s Last name, First name. “Title of Article.” Title of Journal volume number, no. issue number (Year of publication): page numbers.

Example : Brown, LM, Keating, JG, Jones, SM. “The Role of Social Support in Coping with Stress among African American Adolescents.” J Res Adolesc 22, no. 1 (2012): 218-233.

Author’s Last name, First name. “Title of Webpage.” Name of Website. Publication date. Accessed date. URL.

Example : Centers for Disease Control and Prevention. “COVID-19: How to Protect Yourself and Others.” CDC. December 11, 2020. Accessed April 1, 2023. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html.

Author’s Last name, First name. “Title of Article.” Title of Magazine, Month Day, Year of publication, page numbers.

Example : Smith, M. “The Power of Positive Thinking.” Psychology Today, March 1, 2019, 32-35.

Author’s Last name, First name. “Title of Article.” Title of Newspaper, Month Day, Year of publication.

Example : Johnson, B. “New Study Shows Benefits of Exercise on Mental Health.” The New York Times, February 15, 2021.

Editor’s Last name, First name, ed. Title of Book. Place of publication: Publisher, Year of publication.

Example : Thompson, JP, ed. Social Work in the 21st Century. Thousand Oaks, CA: Sage Publications, 2014.

Author’s Last name, First name. “Title of Chapter.” In Title of Book, edited by Editor’s Last name, First name, page numbers. Place of publication: Publisher, Year of publication.

Example : Johnson, KS. “The Future of Social Work: Challenges and Opportunities.” In Social Work in the 21st Century, edited by Thompson, JP, 105-118. Thousand Oaks, CA: Sage Publications, 2014.

IEEE (Institute of Electrical and Electronics Engineers) Style

IEEE (Institute of Electrical and Electronics Engineers) style is commonly used in engineering, computer science, and other technical fields. Here are the different reference formats in IEEE style:

Author’s Last name, First name. Book Title. Place of Publication: Publisher, Year of publication.

Example : Oppenheim, A. V., & Schafer, R. W. Discrete-Time Signal Processing. Upper Saddle River, NJ: Prentice Hall, 2010.

Author’s Last name, First name. “Title of Article.” Abbreviated Journal Title, vol. number, no. issue number, pp. page numbers, Month year of publication.

Example: Shannon, C. E. “A Mathematical Theory of Communication.” Bell System Technical Journal, vol. 27, no. 3, pp. 379-423, July 1948.

Conference paper

Author’s Last name, First name. “Title of Paper.” In Title of Conference Proceedings, Place of Conference, Date of Conference, pp. page numbers, Year of publication.

Example: Gupta, S., & Kumar, P. “An Improved System of Linear Discriminant Analysis for Face Recognition.” In Proceedings of the 2011 International Conference on Computer Science and Network Technology, Harbin, China, Dec. 2011, pp. 144-147.

Author’s Last name, First name. “Title of Webpage.” Name of Website. Date of publication or last update. Accessed date. URL.

Example : National Aeronautics and Space Administration. “Apollo 11.” NASA. July 20, 1969. Accessed April 1, 2023. https://www.nasa.gov/mission_pages/apollo/apollo11.html.

Technical report

Author’s Last name, First name. “Title of Report.” Name of Institution or Organization, Report number, Year of publication.

Example : Smith, J. R. “Development of a New Solar Panel Technology.” National Renewable Energy Laboratory, NREL/TP-6A20-51645, 2011.

Author’s Last name, First name. “Title of Patent.” Patent number, Issue date.

Example : Suzuki, H. “Method of Producing Carbon Nanotubes.” US Patent 7,151,019, December 19, 2006.

Standard Title. Standard number, Publication date.

Example : IEEE Standard for Floating-Point Arithmetic. IEEE Std 754-2008, August 29, 2008

ACS (American Chemical Society) Style

ACS (American Chemical Society) style is commonly used in chemistry and related fields. Here are the different reference formats in ACS style:

Author’s Last name, First name; Author’s Last name, First name. Title of Article. Abbreviated Journal Title Year, Volume, Page Numbers.

Example : Wang, Y.; Zhao, X.; Cui, Y.; Ma, Y. Facile Preparation of Fe3O4/graphene Composites Using a Hydrothermal Method for High-Performance Lithium Ion Batteries. ACS Appl. Mater. Interfaces 2012, 4, 2715-2721.

Author’s Last name, First name. Book Title; Publisher: Place of Publication, Year of Publication.

Example : Carey, F. A. Organic Chemistry; McGraw-Hill: New York, 2008.

Author’s Last name, First name. Chapter Title. In Book Title; Editor’s Last name, First name, Ed.; Publisher: Place of Publication, Year of Publication; Volume number, Chapter number, Page Numbers.

Example : Grossman, R. B. Analytical Chemistry of Aerosols. In Aerosol Measurement: Principles, Techniques, and Applications; Baron, P. A.; Willeke, K., Eds.; Wiley-Interscience: New York, 2001; Chapter 10, pp 395-424.

Author’s Last name, First name. Title of Webpage. Website Name, URL (accessed date).

Example : National Institute of Standards and Technology. Atomic Spectra Database. https://www.nist.gov/pml/atomic-spectra-database (accessed April 1, 2023).

Author’s Last name, First name. Patent Number. Patent Date.

Example : Liu, Y.; Huang, H.; Chen, H.; Zhang, W. US Patent 9,999,999, December 31, 2022.

Author’s Last name, First name; Author’s Last name, First name. Title of Article. In Title of Conference Proceedings, Publisher: Place of Publication, Year of Publication; Volume Number, Page Numbers.

Example : Jia, H.; Xu, S.; Wu, Y.; Wu, Z.; Tang, Y.; Huang, X. Fast Adsorption of Organic Pollutants by Graphene Oxide. In Proceedings of the 15th International Conference on Environmental Science and Technology, American Chemical Society: Washington, DC, 2017; Volume 1, pp 223-228.

AMA (American Medical Association) Style

AMA (American Medical Association) style is commonly used in medical and scientific fields. Here are the different reference formats in AMA style:

Author’s Last name, First name. Article Title. Journal Abbreviation. Year; Volume(Issue):Page Numbers.

Example : Jones, R. A.; Smith, B. C. The Role of Vitamin D in Maintaining Bone Health. JAMA. 2019;321(17):1765-1773.

Author’s Last name, First name. Book Title. Edition number. Place of Publication: Publisher; Year.

Example : Guyton, A. C.; Hall, J. E. Textbook of Medical Physiology. 13th ed. Philadelphia, PA: Saunders; 2015.

Author’s Last name, First name. Chapter Title. In: Editor’s Last name, First name, ed. Book Title. Edition number. Place of Publication: Publisher; Year: Page Numbers.

Example: Rajakumar, K. Vitamin D and Bone Health. In: Holick, M. F., ed. Vitamin D: Physiology, Molecular Biology, and Clinical Applications. 2nd ed. New York, NY: Springer; 2010:211-222.

Author’s Last name, First name. Webpage Title. Website Name. URL. Published date. Updated date. Accessed date.

Example : National Cancer Institute. Breast Cancer Prevention (PDQ®)–Patient Version. National Cancer Institute. https://www.cancer.gov/types/breast/patient/breast-prevention-pdq. Published October 11, 2022. Accessed April 1, 2023.

Author’s Last name, First name. Conference presentation title. In: Conference Title; Conference Date; Place of Conference.

Example : Smith, J. R. Vitamin D and Bone Health: A Meta-Analysis. In: Proceedings of the Annual Meeting of the American Society for Bone and Mineral Research; September 20-23, 2022; San Diego, CA.

Thesis or dissertation

Author’s Last name, First name. Title of Thesis or Dissertation. Degree level [Doctoral dissertation or Master’s thesis]. University Name; Year.

Example : Wilson, S. A. The Effects of Vitamin D Supplementation on Bone Health in Postmenopausal Women [Doctoral dissertation]. University of California, Los Angeles; 2018.

ASCE (American Society of Civil Engineers) Style

The ASCE (American Society of Civil Engineers) style is commonly used in civil engineering fields. Here are the different reference formats in ASCE style:

Author’s Last name, First name. “Article Title.” Journal Title, volume number, issue number (year): page numbers. DOI or URL (if available).

Example : Smith, J. R. “Evaluation of the Effectiveness of Sustainable Drainage Systems in Urban Areas.” Journal of Environmental Engineering, vol. 146, no. 3 (2020): 04020010. https://doi.org/10.1061/(ASCE)EE.1943-7870.0001668.

Example : McCuen, R. H. Hydrologic Analysis and Design. 4th ed. Upper Saddle River, NJ: Pearson Education; 2013.

Author’s Last name, First name. “Chapter Title.” In: Editor’s Last name, First name, ed. Book Title. Edition number. Place of Publication: Publisher; Year: page numbers.

Example : Maidment, D. R. “Floodplain Management in the United States.” In: Shroder, J. F., ed. Treatise on Geomorphology. San Diego, CA: Academic Press; 2013: 447-460.

Author’s Last name, First name. “Paper Title.” In: Conference Title; Conference Date; Location. Place of Publication: Publisher; Year: page numbers.

Example: Smith, J. R. “Sustainable Drainage Systems for Urban Areas.” In: Proceedings of the ASCE International Conference on Sustainable Infrastructure; November 6-9, 2019; Los Angeles, CA. Reston, VA: American Society of Civil Engineers; 2019: 156-163.

Author’s Last name, First name. “Report Title.” Report number. Place of Publication: Publisher; Year.

Example : U.S. Army Corps of Engineers. “Hurricane Sandy Coastal Risk Reduction Program, New York and New Jersey.” Report No. P-15-001. Washington, DC: U.S. Army Corps of Engineers; 2015.

CSE (Council of Science Editors) Style

The CSE (Council of Science Editors) style is commonly used in the scientific and medical fields. Here are the different reference formats in CSE style:

Author’s Last name, First Initial. Middle Initial. “Article Title.” Journal Title. Year;Volume(Issue):Page numbers.

Example : Smith, J.R. “Evaluation of the Effectiveness of Sustainable Drainage Systems in Urban Areas.” Journal of Environmental Engineering. 2020;146(3):04020010.

Author’s Last name, First Initial. Middle Initial. Book Title. Edition number. Place of Publication: Publisher; Year.

Author’s Last name, First Initial. Middle Initial. “Chapter Title.” In: Editor’s Last name, First Initial. Middle Initial., ed. Book Title. Edition number. Place of Publication: Publisher; Year:Page numbers.

Author’s Last name, First Initial. Middle Initial. “Paper Title.” In: Conference Title; Conference Date; Location. Place of Publication: Publisher; Year.

Example : Smith, J.R. “Sustainable Drainage Systems for Urban Areas.” In: Proceedings of the ASCE International Conference on Sustainable Infrastructure; November 6-9, 2019; Los Angeles, CA. Reston, VA: American Society of Civil Engineers; 2019.

Author’s Last name, First Initial. Middle Initial. “Report Title.” Report number. Place of Publication: Publisher; Year.

Bluebook Style

The Bluebook style is commonly used in the legal field for citing legal documents and sources. Here are the different reference formats in Bluebook style:

Case citation

Case name, volume source page (Court year).

Example : Brown v. Board of Education, 347 U.S. 483 (1954).

Statute citation

Name of Act, volume source § section number (year).

Example : Clean Air Act, 42 U.S.C. § 7401 (1963).

Regulation citation

Name of regulation, volume source § section number (year).

Example: Clean Air Act, 40 C.F.R. § 52.01 (2019).

Book citation

Author’s Last name, First Initial. Middle Initial. Book Title. Edition number (if applicable). Place of Publication: Publisher; Year.

Example: Smith, J.R. Legal Writing and Analysis. 3rd ed. New York, NY: Aspen Publishers; 2015.

Journal article citation

Author’s Last name, First Initial. Middle Initial. “Article Title.” Journal Title. Volume number (year): first page-last page.

Example: Garcia, C. “The Right to Counsel: An International Comparison.” International Journal of Legal Information. 43 (2015): 63-94.

Website citation

Author’s Last name, First Initial. Middle Initial. “Page Title.” Website Title. URL (accessed month day, year).

Example : United Nations. “Universal Declaration of Human Rights.” United Nations. https://www.un.org/en/universal-declaration-human-rights/ (accessed January 3, 2023).

Oxford Style

The Oxford style, also known as the Oxford referencing system or the documentary-note citation system, is commonly used in the humanities, including literature, history, and philosophy. Here are the different reference formats in Oxford style:

Author’s Last name, First name. Book Title. Place of Publication: Publisher, Year of Publication.

Example : Smith, John. The Art of Writing. New York: Penguin, 2020.

Author’s Last name, First name. “Article Title.” Journal Title volume, no. issue (year): page range.

Example: Garcia, Carlos. “The Role of Ethics in Philosophy.” Philosophy Today 67, no. 3 (2019): 53-68.

Chapter in an edited book citation

Author’s Last name, First name. “Chapter Title.” In Book Title, edited by Editor’s Name, page range. Place of Publication: Publisher, Year of Publication.

Example : Lee, Mary. “Feminism in the 21st Century.” In The Oxford Handbook of Feminism, edited by Jane Smith, 51-69. Oxford: Oxford University Press, 2018.

Author’s Last name, First name. “Page Title.” Website Title. URL (accessed day month year).

Example : Jones, David. “The Importance of Learning Languages.” Oxford Language Center. https://www.oxfordlanguagecenter.com/importance-of-learning-languages/ (accessed 3 January 2023).

Dissertation or thesis citation

Author’s Last name, First name. “Title of Dissertation/Thesis.” PhD diss., University Name, Year of Publication.

Example : Brown, Susan. “The Art of Storytelling in American Literature.” PhD diss., University of Oxford, 2020.

Newspaper article citation

Author’s Last name, First name. “Article Title.” Newspaper Title, Month Day, Year.

Example : Robinson, Andrew. “New Developments in Climate Change Research.” The Guardian, September 15, 2022.

AAA (American Anthropological Association) Style

The American Anthropological Association (AAA) style is commonly used in anthropology research papers and journals. Here are the different reference formats in AAA style:

Author’s Last name, First name. Year of Publication. Book Title. Place of Publication: Publisher.

Example : Smith, John. 2019. The Anthropology of Food. New York: Routledge.

Author’s Last name, First name. Year of Publication. “Article Title.” Journal Title volume, no. issue: page range.

Example : Garcia, Carlos. 2021. “The Role of Ethics in Anthropology.” American Anthropologist 123, no. 2: 237-251.

Author’s Last name, First name. Year of Publication. “Chapter Title.” In Book Title, edited by Editor’s Name, page range. Place of Publication: Publisher.

Example: Lee, Mary. 2018. “Feminism in Anthropology.” In The Oxford Handbook of Feminism, edited by Jane Smith, 51-69. Oxford: Oxford University Press.

Author’s Last name, First name. Year of Publication. “Page Title.” Website Title. URL (accessed day month year).

Example : Jones, David. 2020. “The Importance of Learning Languages.” Oxford Language Center. https://www.oxfordlanguagecenter.com/importance-of-learning-languages/ (accessed January 3, 2023).

Author’s Last name, First name. Year of Publication. “Title of Dissertation/Thesis.” PhD diss., University Name.

Example : Brown, Susan. 2022. “The Art of Storytelling in Anthropology.” PhD diss., University of California, Berkeley.

Author’s Last name, First name. Year of Publication. “Article Title.” Newspaper Title, Month Day.

Example : Robinson, Andrew. 2021. “New Developments in Anthropology Research.” The Guardian, September 15.

AIP (American Institute of Physics) Style

The American Institute of Physics (AIP) style is commonly used in physics research papers and journals. Here are the different reference formats in AIP style:

Example : Johnson, S. D. 2021. “Quantum Computing and Information.” Journal of Applied Physics 129, no. 4: 043102.

Example : Feynman, Richard. 2018. The Feynman Lectures on Physics. New York: Basic Books.

Example : Jones, David. 2020. “The Future of Quantum Computing.” In The Handbook of Physics, edited by John Smith, 125-136. Oxford: Oxford University Press.

Conference proceedings citation

Author’s Last name, First name. Year of Publication. “Title of Paper.” Proceedings of Conference Name, date and location: page range. Place of Publication: Publisher.

Example : Chen, Wei. 2019. “The Applications of Nanotechnology in Solar Cells.” Proceedings of the 8th International Conference on Nanotechnology, July 15-17, Tokyo, Japan: 224-229. New York: AIP Publishing.

Example : American Institute of Physics. 2022. “About AIP Publishing.” AIP Publishing. https://publishing.aip.org/about-aip-publishing/ (accessed January 3, 2023).

Patent citation

Author’s Last name, First name. Year of Publication. Patent Number.

Example : Smith, John. 2018. US Patent 9,873,644.

References Writing Guide

Here are some general guidelines for writing references:

• Follow the citation style guidelines: Different disciplines and journals may require different citation styles (e.g., APA, MLA, Chicago). It is important to follow the specific guidelines for the citation style required.
• Include all necessary information : Each citation should include enough information for readers to locate the source. For example, a journal article citation should include the author(s), title of the article, journal title, volume number, issue number, page numbers, and publication year.
• Use proper formatting: Citation styles typically have specific formatting requirements for different types of sources. Make sure to follow the proper formatting for each citation.
• Order citations alphabetically: If listing multiple sources, they should be listed alphabetically by the author’s last name.
• Be consistent: Use the same citation style throughout the entire paper or project.
• Check for accuracy: Double-check all citations to ensure accuracy, including correct spelling of author names and publication information.
• Use reputable sources: When selecting sources to cite, choose reputable and authoritative sources. Avoid sources that are biased or unreliable.
• Include all sources: Make sure to include all sources used in the research, including those that were not directly quoted but still informed the work.
• Use online tools : There are online tools available (e.g., citation generators) that can help with formatting and organizing references.

Purpose of References in Research

References in research serve several purposes:

• To give credit to the original authors or sources of information used in the research. It is important to acknowledge the work of others and avoid plagiarism.
• To provide evidence for the claims made in the research. References can support the arguments, hypotheses, or conclusions presented in the research by citing relevant studies, data, or theories.
• To allow readers to find and verify the sources used in the research. References provide the necessary information for readers to locate and access the sources cited in the research, which allows them to evaluate the quality and reliability of the information presented.
• To situate the research within the broader context of the field. References can show how the research builds on or contributes to the existing body of knowledge, and can help readers to identify gaps in the literature that the research seeks to address.

Importance of References in Research

References play an important role in research for several reasons:

• Credibility : By citing authoritative sources, references lend credibility to the research and its claims. They provide evidence that the research is based on a sound foundation of knowledge and has been carefully researched.
• Avoidance of Plagiarism : References help researchers avoid plagiarism by giving credit to the original authors or sources of information. This is important for ethical reasons and also to avoid legal repercussions.
• Reproducibility : References allow others to reproduce the research by providing detailed information on the sources used. This is important for verification of the research and for others to build on the work.
• Context : References provide context for the research by situating it within the broader body of knowledge in the field. They help researchers to understand where their work fits in and how it builds on or contributes to existing knowledge.
• Evaluation : References provide a means for others to evaluate the research by allowing them to assess the quality and reliability of the sources used.

Advantages of References in Research

There are several advantages of including references in research:

• Acknowledgment of Sources: Including references gives credit to the authors or sources of information used in the research. This is important to acknowledge the original work and avoid plagiarism.
• Evidence and Support : References can provide evidence to support the arguments, hypotheses, or conclusions presented in the research. This can add credibility and strength to the research.
• Reproducibility : References provide the necessary information for others to reproduce the research. This is important for the verification of the research and for others to build on the work.
• Context : References can help to situate the research within the broader body of knowledge in the field. This helps researchers to understand where their work fits in and how it builds on or contributes to existing knowledge.
• Evaluation : Including references allows others to evaluate the research by providing a means to assess the quality and reliability of the sources used.
• Ongoing Conversation: References allow researchers to engage in ongoing conversations and debates within their fields. They can show how the research builds on or contributes to the existing body of knowledge.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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• Referencing

Referencing explained

Why and when to reference.

Referencing is an important part of academic work. It puts your work in context, demonstrates the breadth and depth of your research, and acknowledges other people’s work. You should reference whenever you use someone else’s idea.

View video using Microsoft Stream (link opens in a new window, available for University members only)

These webpages explain what referencing is, why it is important and give an overview of the main elements of how to reference. Our Referencing made simple tutorial opens in a new window and covers how to identify your source and create a reference with interactive examples.

Why reference?

Referencing correctly:

• helps you to avoid plagiarism by making it clear which ideas are your own and which are someone else’s
• shows your understanding of the topic
• gives supporting evidence for your ideas, arguments and opinions
• allows others to identify the sources you have used.

When to reference

Whenever you use an idea from someone else's work, for example from a journal article, textbook or website, you should cite the original author to make it clear where that idea came from. This is the case regardless of whether you have paraphrased, summarised or directly quoted their work. This is a key part of good practice in academic writing.

Read more on:

• academic integrity
• quoting, summarising, paraphrasing, and synthesising
• citing direct quotations in Leeds Harvard or citing direct quotations in Leeds Numeric styles.

University and school policies

The University referencing policy (PDF) sets out the referencing requirements that all taught students and tutors are expected to follow.

Each school in the University requires students to use a specific style of referencing. Check the referencing style used in your school before you begin.

All your citations and references should match the style you are using exactly, including any punctuation, capitalisation, italics and bold, and you should use the same referencing style throughout your assignment.

Citing sources: Overview

• Citation style guides

Manage your references

Use these tools to help you organize and cite your references:

• Citation Management and Writing Tools

If you have questions after consulting this guide about how to cite, please contact your advisor/professor or the writing and communication center .

Why citing is important

It's important to cite sources you used in your research for several reasons:

• To show your reader you've done proper research by listing sources you used to get your information
• To be a responsible scholar by giving credit to other researchers and acknowledging their ideas
• To avoid plagiarism by quoting words and ideas used by other authors
• To allow your reader to track down the sources you used by citing them accurately in your paper by way of footnotes, a bibliography or reference list

About citations

Citing a source means that you show, within the body of your text, that you took words, ideas, figures, images, etc. from another place.

Citations are a short way to uniquely identify a published work (e.g. book, article, chapter, web site).  They are found in bibliographies and reference lists and are also collected in article and book databases.

Citations consist of standard elements, and contain all the information necessary to identify and track down publications, including:

• author name(s)
• titles of books, articles, and journals
• date of publication
• page numbers
• volume and issue numbers (for articles)

Citations may look different, depending on what is being cited and which style was used to create them. Choose an appropriate style guide for your needs.  Here is an example of an article citation using four different citation styles.  Notice the common elements as mentioned above:

Author - R. Langer

Article Title - New Methods of Drug Delivery

Source Title - Science

Volume and issue - Vol 249, issue 4976

Publication Date - 1990

Page numbers - 1527-1533

American Chemical Society (ACS) style:

Langer, R. New Methods of Drug Delivery. Science 1990 , 249 , 1527-1533.

IEEE Style:

R. Langer, " New Methods of Drug Delivery," Science , vol. 249 , pp. 1527-1533 , SEP 28, 1990 .

American Psychological Association   (APA) style:

Langer, R. (1990) . New methods of drug delivery. Science , 249 (4976), 1527-1533.

Modern Language Association (MLA) style:

Langer, R. " New Methods of Drug Delivery." Science 249.4976 (1990) : 1527-33.

What to cite

You must cite:

• Facts, figures, ideas, or other information that is not common knowledge

Publications that must be cited include:  books, book chapters, articles, web pages, theses, etc.

Another person's exact words should be quoted and cited to show proper credit 

When in doubt, be safe and cite your source!

Avoiding plagiarism

Plagiarism occurs when you borrow another's words (or ideas) and do not acknowledge that you have done so. In this culture, we consider our words and ideas intellectual property; like a car or any other possession, we believe our words belong to us and cannot be used without our permission.

Plagiarism is a very serious offense. If it is found that you have plagiarized -- deliberately or inadvertently -- you may face serious consequences. In some instances, plagiarism has meant that students have had to leave the institutions where they were studying.

The best way to avoid plagiarism is to cite your sources - both within the body of your paper and in a bibliography of sources you used at the end of your paper.

Some useful links about plagiarism:

• MIT Academic Integrity Overview on citing sources and avoiding plagiarism at MIT.
• Avoiding Plagiarism From the MIT Writing and Communication Center.
• Plagiarism: What It is and How to Recognize and Avoid It From Indiana University's Writing Tutorial Services.
• Plagiarism- Overview A resource from Purdue University.
• Next: Citation style guides >>
• Last Updated: Jan 16, 2024 7:02 AM
• URL: https://libguides.mit.edu/citing

Citing and referencing

What is referencing.

• What is Plagiarism?
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Referencing is a standardized method of formatting the sources you have used in your written works. Any given referencing style serves many purposes: 

• Establishing credibility by citing reliable sources.
• Preventing plagiarism by giving credit to original creators. 
• Building on and connecting with existing knowledge. 
• Enabling verification and reproducibility of research. 
• Abiding and demonstrating intellectual property rights and standards.
• Provide evidence to support your arguments. 
• Acknowledging diverse perspectives and sources in your work. 

1. In-text citations

In-text citations are important, they consist of mentioning a specific source used in the body of the work. The format of the citation may change depending on the style you are using (e.g. MLA, APA, Chicago, etc.), yet there are some basic elements you need to include, which are: 

• Name of the author(s)
• Year of publication

You must add the exact page number in your citation if you used a direct quote from a source. 

2. List of references

This is  a list of the sources you have cited in the text  at the end of your paper. It is not a list of “works consulted”. Every source listed in your references list must also be cited in the body of your work and vice versa. 

• Next: What is Plagiarism? >>
• Last Updated: Apr 25, 2024 8:34 AM
• URL: https://balamand.libguides.com/citing

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A Quick Guide to Harvard Referencing | Citation Examples

Published on 14 February 2020 by Jack Caulfield . Revised on 15 September 2023.

Referencing is an important part of academic writing. It tells your readers what sources you’ve used and how to find them.

Harvard is the most common referencing style used in UK universities. In Harvard style, the author and year are cited in-text, and full details of the source are given in a reference list .

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Table of contents

Harvard in-text citation, creating a harvard reference list, harvard referencing examples, referencing sources with no author or date, frequently asked questions about harvard referencing.

A Harvard in-text citation appears in brackets beside any quotation or paraphrase of a source. It gives the last name of the author(s) and the year of publication, as well as a page number or range locating the passage referenced, if applicable:

Note that ‘p.’ is used for a single page, ‘pp.’ for multiple pages (e.g. ‘pp. 1–5’).

An in-text citation usually appears immediately after the quotation or paraphrase in question. It may also appear at the end of the relevant sentence, as long as it’s clear what it refers to.

When your sentence already mentions the name of the author, it should not be repeated in the citation:

Sources with multiple authors

When you cite a source with up to three authors, cite all authors’ names. For four or more authors, list only the first name, followed by ‘ et al. ’:

Sources with no page numbers

Some sources, such as websites , often don’t have page numbers. If the source is a short text, you can simply leave out the page number. With longer sources, you can use an alternate locator such as a subheading or paragraph number if you need to specify where to find the quote:

Multiple citations at the same point

When you need multiple citations to appear at the same point in your text – for example, when you refer to several sources with one phrase – you can present them in the same set of brackets, separated by semicolons. List them in order of publication date:

Multiple sources with the same author and date

If you cite multiple sources by the same author which were published in the same year, it’s important to distinguish between them in your citations. To do this, insert an ‘a’ after the year in the first one you reference, a ‘b’ in the second, and so on:

Prevent plagiarism, run a free check.

A bibliography or reference list appears at the end of your text. It lists all your sources in alphabetical order by the author’s last name, giving complete information so that the reader can look them up if necessary.

The reference entry starts with the author’s last name followed by initial(s). Only the first word of the title is capitalised (as well as any proper nouns).

Sources with multiple authors in the reference list

As with in-text citations, up to three authors should be listed; when there are four or more, list only the first author followed by ‘ et al. ’:

Reference list entries vary according to source type, since different information is relevant for different sources. Formats and examples for the most commonly used source types are given below.

• Entire book
• Book chapter
• Translated book
• Edition of a book

Journal articles

• Print journal
• Online-only journal with DOI
• Online-only journal with no DOI
• General web page
• Online article or blog
• Social media post

Sometimes you won’t have all the information you need for a reference. This section covers what to do when a source lacks a publication date or named author.

No publication date

When a source doesn’t have a clear publication date – for example, a constantly updated reference source like Wikipedia or an obscure historical document which can’t be accurately dated – you can replace it with the words ‘no date’:

Note that when you do this with an online source, you should still include an access date, as in the example.

When a source lacks a clearly identified author, there’s often an appropriate corporate source – the organisation responsible for the source – whom you can credit as author instead, as in the Google and Wikipedia examples above.

When that’s not the case, you can just replace it with the title of the source in both the in-text citation and the reference list:

Harvard referencing uses an author–date system. Sources are cited by the author’s last name and the publication year in brackets. Each Harvard in-text citation corresponds to an entry in the alphabetised reference list at the end of the paper.

Vancouver referencing uses a numerical system. Sources are cited by a number in parentheses or superscript. Each number corresponds to a full reference at the end of the paper.

A Harvard in-text citation should appear in brackets every time you quote, paraphrase, or refer to information from a source.

The citation can appear immediately after the quotation or paraphrase, or at the end of the sentence. If you’re quoting, place the citation outside of the quotation marks but before any other punctuation like a comma or full stop.

In Harvard referencing, up to three author names are included in an in-text citation or reference list entry. When there are four or more authors, include only the first, followed by ‘ et al. ’

Though the terms are sometimes used interchangeably, there is a difference in meaning:

• A reference list only includes sources cited in the text – every entry corresponds to an in-text citation .
• A bibliography also includes other sources which were consulted during the research but not cited.

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the ‘Cite this Scribbr article’ button to automatically add the citation to our free Reference Generator.

Caulfield, J. (2023, September 15). A Quick Guide to Harvard Referencing | Citation Examples. Scribbr. Retrieved 21 May 2024, from https://www.scribbr.co.uk/referencing/harvard-style/

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Articles, Books and . . . ? Understanding the Many Types of Information Found in Libraries

• Reference Sources

Encyclopedias

Dictionaries, almanacs and yearbooks, handbooks and manuals.

• Documents and Reports
• Non-Text Content
• Archival Materials

Reference sources are generally the place to begin your research, especially when you're starting out with an unfamiliar field. But they're also where you return when you need to look up formulas, facts, definitions, and other standard details; they tend to pack a lot of information into simple, easy-to-use packages.

Physical Media

Many reference works are available online and are accessible through links from the Library Catalog and from subject or course guides , but many valuable reference resources are still available only in print, and a few highly specialized tools are on microform or CD. Because print-only reference books are in high demand, they are kept in separate, non-circulating reference collections in most UCLA libraries.

Scholarly Sources

Reference sources are rarely peer-reviewed. In fact, because they mostly contain established, factual information, they're sometimes not even cited in academic works, unless directly quoted. Check your style manual for best guidelines.

Primary or Secondary Sources

As compilations of existing information, reference works are decisively in the category of secondary sources... to the point that some people call them tertiary sources .

Encyclopedias attempt to provide comprehensive summaries of knowledge in either a specific field (subject encyclopedias) or "everything" (general encyclopedias). Encyclopedias are typically divided into a collection of articles on discrete topics. Academically oriented encyclopedias will often include short bibliographies, making them a good resource for identifying key books and articles on a topic.

• Online Encyclopedias
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• Subject dictionaries: define technical terms in specific fields, sometimes in as much detail as an encyclopedia
• Bilingual dictionaries: define words in a different language
• Thesauri: provide synonyms
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• Major Online Dictionaries
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Both "handbook" and "manual" refer to the traditional small size of the volumes, designed to fit in one hand for ease of use. Despite this origin, many modern handbooks are quite hefty!

• Databases containing online handbooks
• Find print handbooks in the Library Catalog Search "[subject] handbooks" within Subject List.
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• Research Process
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• Find Sources through the Library
• Evaluate Your Info
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• Evaluate, Write & Cite

• is the right thing to do  to give credit to those who had the idea
• shows that you have read and understand  what experts have had to say about your topic
• helps people find the sources  that you used in case they want to read more about the topic
• provides   evidence  for your arguments
• is professional and  standard practice   for students and scholars

What is a Citation?

A citation identifies for the reader the original source for an idea, information, or image that is referred to in a work.

• In the body of a paper, the  in-text citation  acknowledges the source of information used.
• At the end of a paper, the citations are compiled on a  References  or  Works Cited  list. A basic citation includes the author, title, and publication information of the source. 

From:  Lemieux  Library,  University  of Seattle 

Why Should You Cite?

Quoting Are you quoting two or more consecutive words from a source? Then the original source should be cited and the words or phrase placed in quotes. 

Paraphrasing If an idea or information comes from another source,  even if you put it in your own words , you still need to credit the source.  General vs. Unfamiliar Knowledge You do not need to cite material which is accepted common knowledge. If in doubt whether your information is common knowledge or not, cite it. Formats We usually think of books and articles. However, if you use material from web sites, films, music, graphs, tables, etc. you'll also need to cite these as well.

Plagiarism is presenting the words or ideas of someone else as your own without proper acknowledgment of the source. When you work on a research paper and use supporting material from works by others, it's okay to quote people and use their ideas, but you do need to correctly credit them. Even when you summarize or paraphrase information found in books, articles, or Web pages, you must acknowledge the original author.

Citation Style Help

Helpful links:

• MLA ,  Works Cited : A Quick Guide (a template of core elements)
• CSE  (Council of Science Editors)

For additional writing resources specific to styles listed here visit the  Purdue OWL Writing Lab

Citation and Bibliography Resources

• How to Write an Annotated Bibliography
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Creative Commons Attribution 3.0 License except where otherwise noted.

Land Acknowledgement

The land on which we gather is the unceded territory of the Awaswas-speaking Uypi Tribe. The Amah Mutsun Tribal Band, comprised of the descendants of indigenous people taken to missions Santa Cruz and San Juan Bautista during Spanish colonization of the Central Coast, is today working hard to restore traditional stewardship practices on these lands and heal from historical trauma.

The land acknowledgement used at UC Santa Cruz was developed in partnership with the Amah Mutsun Tribal Band Chairman and the Amah Mutsun Relearning Program at the UCSC Arboretum .

APA Style 7th Edition: Citing Your Sources

• Basics of APA Formatting
• In Text Quick View
• Block Quotes

The Generic Reference

• Books & eBooks
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References appear at the end of your document and follow a Who, When, What and Where format.  Only include sources you cited within your research document (*exception for personal communications which are excluded from the reference list).

Who:  Identify the creator of the source.  Who can be: a single author; multiple authors; an organization or corporation; editor/s; or the director and producer.  On some occasions when authorship cannot be attributed then you revert to the title entry formatting. 

When:   Identify when the source was published.  For most source types,  simply provide a year of publication.  Exceptions as follows: year followed by month for papers and posters presented at conferences; year followed by month and date for blogs, social media, newspaper and magazine publications.  When there is no publication date (common for web documents and other content) use the abbreviation n.d. for "no date."

What: Title of the source.  This is the title identified for the individual source, rather than where the source is published.  For articles, you want to identify the title of the article rather than the Journal name.  The same can be said for the title of a newspaper article vs. the newspaper name or the title of a webpage vs. the website name.  (ex.  "Mission statement" is a page title on the APA website).

Where:   Once you identify the Who, When, and What, the rest of the information provided to complete the reference falls under "Where."  This portion of the reference sees variations in information included based on source type.  Essentially, it will provide information as to where the reader can retrieve the source.  Where can fall under 2 broad categories: works part of a great whole and stand-alone sources.

Visit the individual Reference Type pages to see further formatting and examples for your source type.

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Academic writing relies on more than just the ideas and experience of one author. It also uses the ideas and research of other sources: books, journal articles, websites, and so forth. These other sources may be used to support the author's ideas, or the author may be discussing, analysing, or critiquing other sources.

Referencing is used to tell the reader where ideas from other sources have been used in an assignment. There are many reasons why it is important to reference sources correctly:

• It shows the reader that you can find and use sources to create a solid argument
• It properly credits the originators of ideas, theories, and research findings
• It shows the reader how your argument relates to the big picture

(For a detailed discussion, see why reference? )

Failure to properly acknowledge sources is called plagiarism , and it can carry significant academic penalties. Fortunately, plagiarism is easy to avoid by following a few basic principles.

What needs to be referenced?

Whenever an assignment uses words, facts, ideas, theories, or interpretations from other sources, those sources must be referenced. Referencing is needed when:

• You have copied words from a book, article, or other source exactly ( quotation )
• You have used an idea or fact from an outside source, even if you haven't used their exact wording ( paraphrasing and summarising )

The only exception to this is when the information is common knowledge , which is something that anyone is likely to know. If you are uncertain whether to reference something or not, it is better to reference it.

Citations and references

There are two elements used in referencing:

• A citation in the text of the assignment (also known as in-text citations)
• An entry in a reference list at the end of the assignment

The citation contains only enough information for the reader to find the source in the reference list. Usually, this is the name of the source's author and the year the source was published. For example:

When testing the usability of a website, it is necessary to gather demographic information about the users (Lazar, 2006).

In this example, (Lazar, 2006) tells the reader that this information has come from a source written by Lazar, which was published in 2006. This is a signpost, pointing the reader to the reference list.

The reference list is a list of all the sources used (and cited) in an assignment. It is alphabetised according to the names of the authors. Each entry in the reference list contains detailed information about one source. This usually includes the author's name, the year of publication, the title of the source, and source location details (e.g., publisher’s name, URL). For example:

Durie, M. (2003). Ngā kāhui pou: Launching Māori futures . Huia.

Hazledine, T., & Quiggan, J. (2006). Public policy in Australia and New Zealand: The new global context. Australian Journal of Political Science, 41 (2), 131–143.

Lazar, J. (2006). Web usability: A user-centered design approach . Pearson Addison Wesley.

Ministry for Primary Industries. (2012).  Food safety . https://www.mpi.govt.nz/food-safety

If they wanted to, a reader could use this information to find these sources in a library or online.

Referencing is a formal system: there are rules and standards to follow when formatting citations and references. Many students find referencing quite intimidating at first. Like any skill, it takes time and patience to learn.

The examples above use APA style , a format created by the American Psychological Association. It is the most common referencing style used at Massey University.

Other styles include MLA style , Oxford style , Harvard style , and Chicago style . These styles are subtly different, and different colleges and departments may ask you to use different styles. Oxford style, for example, uses footnotes instead of in-text citations, and a bibliography instead of a reference list .

For more about the different referencing styles used at Massey University, see referencing styles .

Have a study or assignment writing question? Ask an expert at Academic Q+A forum

Get feedback on your draft assignment at Academic Writing and Learning Support

Need help with your assignment or referencing? Contact a consultant and receive online and/or face-to-face support

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How Do I Reference?

Referencing and Avoiding Plagiarism

• First Online: 19 October 2023

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• Sue Reeves   ORCID: orcid.org/0000-0002-3017-0559 3 &
• Bartek Buczkowski   ORCID: orcid.org/0000-0002-4146-3664 4  

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References are an important part of your dissertation, and you may need anywhere between 20 and 200 references, possibly more depending on the length of your thesis. But it is important that you reference appropriately and correctly, whether this is in the in-text citations or the list of references at the end of your thesis. This chapter explains the differences between a reference list and a bibliography. You will also want to avoid the risk of plagiarism, and this is explained, to help you ensure that you write your dissertation entirely in your own words.

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Understanding a reference: Working out what it is

When conducting library research, you will often need to find material based on the information in a reference list or reading list. In order to then locate that source, you will need to understand what the different elements of the reference mean and identify what type of source it is.

A reference is made up of some key details/elements about the source, that can broadly be broken down into the following:

• Who has ‘made’ the item (the author, creator, compiler…)?
• What is it called?
• If part of a larger work, what is that called?
• Where was (is) it disseminated/published?
• Who is responsible for the dissemination / publishing?
• When was it disseminated / published?
• A direct quotation, or allusion, should always include the page number(s).

You can normally identify the type of source by the information presented in the reference. Here are some tips for identifying some of the key types of source that you might come across on a reading/reference list:

Cooke, A. (2001) A guide to finding quality information on the Internet: selection and evaluation strategies. 2nd ed. London: Library Association Publishing.

Note the edition information, the publisher location (London) and publisher name (Library Association Publishing) which are included in the reference.

Journal article

De Pinto, M., Jelacic, J., Edwards, W.T. (2008) Very-low-dose ketamine for the management of pain and sedation in the ICU. Acute pain [online], 10 (2), p. 100. Available at: doi:10.1016/j.acpain.2008.05.023 [Accessed 8 September 2008].

Note that the title of both the article ('Very low dose ketamine ... ') and the journal ('Acute pain') are included. The journal volume (10) and issue number (2) are also included.

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Referencing

Referencing is one of the most important aspects of any academic research and poor or lack of referencing will not only diminish your marks, but such practices may also be perceived as plagiarism by your university and disciplinary actions may follow that may even result in expulsion from the course.

Difference between References and Bibliography

It is very important to be able to distinguish between References and Bibliography. Under References you list resources that you referred to within the body of the work that also include quotations.  For example,

It has been noted that “time and the management of time is an important issue, and the supply of time management products – books, articles, CDs, workshops, etc. – reflects the huge demand for these products” (Walsh, 2007, p.3).

Interchangeability of identical parts and a high level of straightforwardness of attaching these parts through the assembly line can be considered as revolutionary components of Fordism for the first part of the 20 th century (Nolan, 2008).

Under Bibliography, on the other hand, you need to list resources that you have read during the research process in order to widen your knowledge about the research area , but specific piece of information from these resources have not been used in your research in the direct manner. You do not need to refer to Bibliography within the body of the text.

There are various methods of referencing such as Harvard, APA and Vancouver referencing systems. You should check with your dissertation handbook for the exact type of referencing required and follow this requirement thoroughly.

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Citing Sources: What are citations and why should I use them?

What is a citation.

Citations are a way of giving credit when certain material in your work came from another source. It also gives your readers the information necessary to find that source again-- it provides an important roadmap to your research process. Whenever you use sources such as books, journals or websites in your research, you must give credit to the original author by citing the source. 

Why do researchers cite?

Scholarship is a conversation  and scholars use citations not only to  give credit  to original creators and thinkers, but also to  add strength and authority  to their own work.  By citing their sources, scholars are  placing their work in a specific context  to show where they “fit” within the larger conversation.  Citations are also a great way to  leave a trail  intended to help others who may want to explore the conversation or use the sources in their own work.

In short, citations

(1) give credit

(2) add strength and authority to your work

(3) place your work in a specific context

(4) leave a trail for other scholars

"Good citations should reveal your sources, not conceal them. They should honeslty reflect the research you conducted." (Lipson 4)

Lipson, Charles. "Why Cite?"  Cite Right: A Quick Guide to Citation Styles--MLA, APA, Chicago, the Sciences, Professions, and More . Chicago: U of Chicago, 2006. Print.

What does a citation look like?

Different subject disciplines call for citation information to be written in very specific order, capitalization, and punctuation. There are therefore many different style formats. Three popular citation formats are MLA Style (for humanities articles) and APA or Chicago (for social sciences articles).

MLA style (print journal article):  

Whisenant, Warren A. "How Women Have Fared as Interscholastic Athletic Administrators Since the Passage of Title IX." Sex Roles Vol. 49.3 (2003): 179-182.

APA style (print journal article):

Whisenant, W. A. (2003) How Women Have Fared as Interscholastic Athletic Administrators Since the Passage of Title IX. Sex Roles , 49 (3), 179-182.

Chicago style (print journal article):

Whisenant, Warren A. "How Women Have Fared as Interscholastic Athletic Administrators Since the Passage of Title IX." Sex Roles 49, no. 3 (2003): 179-182.

No matter which style you use, all citations require the same basic information:

• Author or Creator
• Container (e.g., Journal or magazine, website, edited book)
• Date of creation or publication
• Publisher 

You are most likely to have easy access to all of your citation information when you find it in the first place. Take note of this information up front, and it will be much easier to cite it effectively later.

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Reference List: Common Reference List Examples

Article (with doi).

Alvarez, E., & Tippins, S. (2019). Socialization agents that Puerto Rican college students use to make financial decisions. Journal of Social Change , 11 (1), 75–85. https://doi.org/10.5590/JOSC.2019.11.1.07

Laplante, J. P., & Nolin, C. (2014). Consultas and socially responsible investing in Guatemala: A case study examining Maya perspectives on the Indigenous right to free, prior, and informed consent. Society & Natural Resources , 27 , 231–248. https://doi.org/10.1080/08941920.2013.861554

Use the DOI number for the source whenever one is available. DOI stands for "digital object identifier," a number specific to the article that can help others locate the source. In APA 7, format the DOI as a web address. Active hyperlinks for DOIs and URLs should be used for documents meant for screen reading. Present these hyperlinks in blue and underlined text (the default formatting in Microsoft Word), although plain black text is also acceptable. Be consistent in your formatting choice for DOIs and URLs throughout your reference list. Also see our Quick Answer FAQ, "Can I use the DOI format provided by library databases?"

Jerrentrup, A., Mueller, T., Glowalla, U., Herder, M., Henrichs, N., Neubauer, A., & Schaefer, J. R. (2018). Teaching medicine with the help of “Dr. House.” PLoS ONE , 13 (3), Article e0193972. https://doi.org/10.1371/journal.pone.0193972

For journal articles that are assigned article numbers rather than page ranges, include the article number in place of the page range.

For more on citing electronic resources, see  Electronic Sources References .

Article (Without DOI)

Found in a common academic research database or in print.

Casler , T. (2020). Improving the graduate nursing experience through support on a social media platform. MEDSURG Nursing , 29 (2), 83–87.

If an article does not have a DOI and you retrieved it from a common academic research database through the university library, there is no need to include any additional electronic retrieval information. The reference list entry looks like the entry for a print copy of the article. (This format differs from APA 6 guidelines that recommended including the URL of a journal's homepage when the DOI was not available.) Note that APA 7 has additional guidance on reference list entries for articles found only in specific databases or archives such as Cochrane Database of Systematic Reviews, UpToDate, ProQuest Dissertations and Theses Global, and university archives. See APA 7, Section 9.30 for more information.

Found on an Open Access Website

Eaton, T. V., & Akers, M. D. (2007). Whistleblowing and good governance. CPA Journal , 77 (6), 66–71. http://archives.cpajournal.com/2007/607/essentials/p58.htm

Provide the direct web address/URL to a journal article found on the open web, often on an open access journal's website. In APA 7, active hyperlinks for DOIs and URLs should be used for documents meant for screen reading. Present these hyperlinks in blue and underlined text (the default formatting in Microsoft Word), although plain black text is also acceptable. Be consistent in your formatting choice for DOIs and URLs throughout your reference list.

Weinstein, J. A. (2010).  Social change  (3rd ed.). Rowman & Littlefield.

If the book has an edition number, include it in parentheses after the title of the book. If the book does not list any edition information, do not include an edition number. The edition number is not italicized.

American Nurses Association. (2015). Nursing: Scope and standards of practice (3rd ed.).

If the author and publisher are the same, only include the author in its regular place and omit the publisher.

Lencioni, P. (2012). The advantage: Why organizational health trumps everything else in business . Jossey-Bass. https://amzn.to/343XPSJ

As a change from APA 6 to APA 7, it is no longer necessary to include the ebook format in the title. However, if you listened to an audiobook and the content differs from the text version (e.g., abridged content) or your discussion highlights elements of the audiobook (e.g., narrator's performance), then note that it is an audiobook in the title element in brackets. For ebooks and online audiobooks, also include the DOI number (if available) or nondatabase URL but leave out the electronic retrieval element if the ebook was found in a common academic research database, as with journal articles. APA 7 allows for the shortening of long DOIs and URLs, as shown in this example. See APA 7, Section 9.36 for more information.

Chapter in an Edited Book

Poe, M. (2017). Reframing race in teaching writing across the curriculum. In F. Condon & V. A. Young (Eds.), Performing antiracist pedagogy in rhetoric, writing, and communication (pp. 87–105). University Press of Colorado.

Include the page numbers of the chapter in parentheses after the book title.

Christensen, L. (2001). For my people: Celebrating community through poetry. In B. Bigelow, B. Harvey, S. Karp, & L. Miller (Eds.), Rethinking our classrooms: Teaching for equity and justice (Vol. 2, pp. 16–17). Rethinking Schools.

Also include the volume number or edition number in the parenthetical information after the book title when relevant.

Freud, S. (1961). The ego and the id. In J. Strachey (Ed.),  The standard edition of the complete psychological works of Sigmund Freud  (Vol. 19, pp. 3-66). Hogarth Press. (Original work published 1923)

When a text has been republished as part of an anthology collection, after the author’s name include the date of the version that was read. At the end of the entry, place the date of the original publication inside parenthesis along with the note “original work published.” For in-text citations of republished work, use both dates in the parenthetical citation, original date first with a slash separating the years, as in this example: Freud (1923/1961). For more information on reprinted or republished works, see APA 7, Sections 9.40-9.41.

Classroom Resources

Citing classroom resources.

If you need to cite content found in your online classroom, use the author (if there is one listed), the year of publication (if available), the title of the document, and the main URL of Walden classrooms. For example, you are citing study notes titled "Health Effects of Exposure to Forest Fires," but you do not know the author's name, your reference entry will look like this:

Health effects of exposure to forest fires [Lecture notes]. (2005). Walden University Canvas. https://waldenu.instructure.com

If you do know the author of the document, your reference will look like this:

Smith, A. (2005). Health effects of exposure to forest fires [PowerPoint slides]. Walden University Canvas. https://waldenu.instructure.com  

A few notes on citing course materials:

• [Lecture notes]
• [Course handout]
• [Study notes]
• It can be difficult to determine authorship of classroom documents. If an author is listed on the document, use that. If the resource is clearly a product of Walden (such as the course-based videos), use Walden University as the author. If you are unsure or if no author is indicated, place the title in the author spot, as above.
• If you cannot determine a date of publication, you can use n.d. (for "no date") in place of the year.

Note:  The web location for Walden course materials is not directly retrievable without a password, and therefore, following APA guidelines, use the main URL for the class sites: https://class.waldenu.edu.

Citing Tempo Classroom Resources

Clear author: 

Smith, A. (2005). Health effects of exposure to forest fires [PowerPoint slides]. Walden University Brightspace. https://mytempo.waldenu.edu

Unclear author:

Health effects of exposure to forest fires [Lecture notes]. (2005). Walden University Brightspace. https://mytempo.waldenu.edu

Conference Sessions and Presentations

Feinman, Y. (2018, July 27). Alternative to proctoring in introductory statistics community college courses [Poster presentation]. Walden University Research Symposium, Minneapolis, MN, United States. https://scholarworks.waldenu.edu/symposium2018/23/

Torgerson, K., Parrill, J., & Haas, A. (2019, April 5-9). Tutoring strategies for online students [Conference session]. The Higher Learning Commission Annual Conference, Chicago, IL, United States. http://onlinewritingcenters.org/scholarship/torgerson-parrill-haas-2019/

Dictionary Entry

Merriam-Webster. (n.d.). Leadership. In Merriam-Webster.com dictionary . Retrieved May 28, 2020, from https://www.merriam-webster.com/dictionary/leadership

When constructing a reference for an entry in a dictionary or other reference work that has no byline (i.e., no named individual authors), use the name of the group—the institution, company, or organization—as author (e.g., Merriam Webster, American Psychological Association, etc.). The name of the entry goes in the title position, followed by "In" and the italicized name of the reference work (e.g., Merriam-Webster.com dictionary , APA dictionary of psychology ). In this instance, APA 7 recommends including a retrieval date as well for this online source since the contents of the page change over time. End the reference entry with the specific URL for the defined word.

Discussion Board Post

Osborne, C. S. (2010, June 29). Re: Environmental responsibility [Discussion post]. Walden University Canvas.  https://waldenu.instructure.com  

Dissertations or Theses

Retrieved From a Database

Nalumango, K. (2019). Perceptions about the asylum-seeking process in the United States after 9/11 (Publication No. 13879844) [Doctoral dissertation, Walden University]. ProQuest Dissertations and Theses.

Retrieved From an Institutional or Personal Website

Evener. J. (2018). Organizational learning in libraries at for-profit colleges and universities [Doctoral dissertation, Walden University]. ScholarWorks. https://scholarworks.waldenu.edu/cgi/viewcontent.cgi?article=6606&context=dissertations

Unpublished Dissertation or Thesis

Kirwan, J. G. (2005). An experimental study of the effects of small-group, face-to-face facilitated dialogues on the development of self-actualization levels: A movement towards fully functional persons [Unpublished doctoral dissertation]. Saybrook Graduate School and Research Center.

For further examples and information, see APA 7, Section 10.6.

Legal Material

For legal references, APA follows the recommendations of The Bluebook: A Uniform System of Citation , so if you have any questions beyond the examples provided in APA, seek out that resource as well.

Court Decisions

Reference format:

Name v. Name, Volume Reporter Page (Court Date). URL

Sample reference entry:

Brown v. Board of Education, 347 U.S. 483 (1954). https://www.oyez.org/cases/1940-1955/347us483

Sample citation:

In Brown v. Board of Education (1954), the Supreme Court ruled racial segregation in schools unconstitutional.

Note: Italicize the case name when it appears in the text of your paper.

Name of Act, Title Source § Section Number (Year). URL

Sample reference entry for a federal statute:

Individuals With Disabilities Education Act, 20 U.S.C. § 1400 et seq. (2004). https://www.congress.gov/108/plaws/publ446/PLAW-108publ446.pdf

Sample reference entry for a state statute:

Minnesota Nurse Practice Act, Minn. Stat. §§ 148.171 et seq. (2019). https://www.revisor.mn.gov/statutes/cite/148.171

Sample citation: Minnesota nurses must maintain current registration in order to practice (Minnesota Nurse Practice Act, 2010).

Note: The § symbol stands for "section." Use §§ for sections (plural). To find this symbol in Microsoft Word, go to "Insert" and click on Symbol." Look in the Latin 1-Supplement subset. Note: U.S.C. stands for "United States Code." Note: The Latin abbreviation " et seq. " means "and what follows" and is used when the act includes the cited section and ones that follow. Note: List the chapter first followed by the section or range of sections.

Unenacted Bills and Resolutions

(Those that did not pass and become law)

Title [if there is one], bill or resolution number, xxx Cong. (year). URL

Sample reference entry for Senate bill:

Anti-Phishing Act, S. 472, 109th Cong. (2005). https://www.congress.gov/bill/109th-congress/senate-bill/472

Sample reference entry for House of Representatives resolution:

Anti-Phishing Act, H.R. 1099, 109th Cong. (2005). https://www.congress.gov/bill/109th-congress/house-bill/1099

The Anti-Phishing Act (2005) proposed up to 5 years prison time for people running Internet scams.

These are the three legal areas you may be most apt to cite in your scholarly work. For more examples and explanation, see APA 7, Chapter 11.

Magazine Article

Clay, R. (2008, June). Science vs. ideology: Psychologists fight back about the misuse of research. Monitor on Psychology , 39 (6). https://www.apa.org/monitor/2008/06/ideology

Note that for citations, include only the year: Clay (2008). For magazine articles retrieved from a common academic research database, leave out the URL. For magazine articles from an online news website that is not an online version of a print magazine, follow the format for a webpage reference list entry.

Newspaper Article (Retrieved Online)

Baker, A. (2014, May 7). Connecticut students show gains in national tests. New York Times . http://www.nytimes.com/2014/05/08/nyregion/national-assessment-of-educational-progress-results-in-Connecticut-and-New-Jersey.html

Include the full date in the format Year, Month Day. Do not include a retrieval date for periodical sources found on websites. Note that for citations, include only the year: Baker (2014). For newspaper articles retrieved from a common academic research database, leave out the URL. For newspaper articles from an online news website that is not an online version of a print newspaper, follow the format for a webpage reference list entry.

OASIS Resources

Oasis webpage.

OASIS. (n.d.). Common reference list examples . Walden University. https://academicguides.waldenu.edu/writingcenter/apa/references/examples

For all OASIS content, list OASIS as the author. Because OASIS webpages do not include publication dates, use “n.d.” for the year.

Interactive Guide

OASIS. (n.d.). Embrace iterative research and writing [Interactive guide]. Walden University. https://academics.waldenu.edu/oasis/iterative-research-writing-web

For OASIS multimedia resources, such as interactive guides, include a description of the resource in brackets after the title.

Online Video/Webcast

Walden University. (2013).  An overview of learning  [Video]. Walden University Canvas.  https://waldenu.instructure.com  

Use this format for online videos such as Walden videos in classrooms. Most of our classroom videos are produced by Walden University, which will be listed as the author in your reference and citation. Note: Some examples of audiovisual materials in the APA manual show the word “Producer” in parentheses after the producer/author area. In consultation with the editors of the APA manual, we have determined that parenthetical is not necessary for the videos in our courses. The manual itself is unclear on the matter, however, so either approach should be accepted. Note that the speaker in the video does not appear in the reference list entry, but you may want to mention that person in your text. For instance, if you are viewing a video where Tobias Ball is the speaker, you might write the following: Tobias Ball stated that APA guidelines ensure a consistent presentation of information in student papers (Walden University, 2013). For more information on citing the speaker in a video, see our page on Common Citation Errors .

Taylor, R. [taylorphd07]. (2014, February 27). Scales of measurement [Video]. YouTube. https://www.youtube.com/watch?v=PDsMUlexaMY

OASIS. (2020, April 15). One-way ANCOVA: Introduction [Video]. YouTube. https://youtu.be/_XnNDQ5CNW8

For videos from streaming sites, use the person or organization who uploaded the video in the author space to ensure retrievability, whether or not that person is the speaker in the video. A username can be provided in square brackets. As a change from APA 6 to APA 7, include the publisher after the title, and do not use "Retrieved from" before the URL. See APA 7, Section 10.12 for more information and examples.

See also reference list entry formats for TED Talks .

Technical and Research Reports

Edwards, C. (2015). Lighting levels for isolated intersections: Leading to safety improvements (Report No. MnDOT 2015-05). Center for Transportation Studies. http://www.cts.umn.edu/Publications/ResearchReports/reportdetail.html?id=2402

Technical and research reports by governmental agencies and other research institutions usually follow a different publication process than scholarly, peer-reviewed journals. However, they present original research and are often useful for research papers. Sometimes, researchers refer to these types of reports as gray literature , and white papers are a type of this literature. See APA 7, Section 10.4 for more information.

Reference list entires for TED Talks follow the usual guidelines for multimedia content found online. There are two common places to find TED talks online, with slightly different reference list entry formats for each.

TED Talk on the TED website

If you find the TED Talk on the TED website, follow the format for an online video on an organizational website:

Owusu-Kesse, K. (2020, June). 5 needs that any COVID-19 response should meet [Video]. TED Conferences. https://www.ted.com/talks/kwame_owusu_kesse_5_needs_that_any_covid_19_response_should_meet

The speaker is the author in the reference list entry if the video is posted on the TED website. For citations, use the speaker's surname.

TED Talk on YouTube

If you find the TED Talk on YouTube or another streaming video website, follow the usual format for streaming video sites:

TED. (2021, February 5). The shadow pandemic of domestic violence during COVID-19 | Kemi DaSilvalbru [Video]. YouTube. https://www.youtube.com/watch?v=PGdID_ICFII

TED is the author in the reference list entry if the video is posted on YouTube since it is the channel on which the video is posted. For citations, use TED as the author.

Walden University Course Catalog

To include the Walden course catalog in your reference list, use this format:

Walden University. (2020). 2019-2020 Walden University catalog . https://catalog.waldenu.edu/index.php

If you cite from a specific portion of the catalog in your paper, indicate the appropriate section and paragraph number in your text:

...which reflects the commitment to social change expressed in Walden University's mission statement (Walden University, 2020, Vision, Mission, and Goals section, para. 2).

And in the reference list:

Walden University. (2020). Vision, mission, and goals. In 2019-2020 Walden University catalog. https://catalog.waldenu.edu/content.php?catoid=172&navoid=59420&hl=vision&returnto=search

Vartan, S. (2018, January 30). Why vacations matter for your health . CNN. https://www.cnn.com/travel/article/why-vacations-matter/index.html

For webpages on the open web, include the author, date, webpage title, organization/site name, and URL. (There is a slight variation for online versions of print newspapers or magazines. For those sources, follow the models in the previous sections of this page.)

American Federation of Teachers. (n.d.). Community schools . http://www.aft.org/issues/schoolreform/commschools/index.cfm

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• 15 May 2024

‘Quantum internet’ demonstration in cities is most advanced yet

• Davide Castelvecchi

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You have full access to this article via your institution.

A quantum network node at Delft University of Technology in the Netherlands. Credit: Marieke de Lorijn for QuTech

Three separate research groups have demonstrated quantum entanglement — in which two or more objects are linked so that they contain the same information even if they are far apart — over several kilometres of existing optical fibres in real urban areas. The feat is a key step towards a future quantum internet , a network that could allow information to be exchanged while encoded in quantum states.

Together, the experiments are “the most advanced demonstrations so far” of the technology needed for a quantum internet, says physicist Tracy Northup at the University of Innsbruck in Austria. Each of the three research teams — based in the United States, China and the Netherlands — was able to connect parts of a network using photons in the optical-fibre-friendly infrared part of the spectrum, which is a “major milestone”, says fellow Innsbruck physicist Simon Baier.

How to build a quantum internet

A quantum internet could enable any two users to establish almost unbreakable cryptographic keys to protect sensitive information . But full use of entanglement could do much more, such as connecting separate quantum computers into one larger, more powerful machine. The technology could also enable certain types of scientific experiment, for example by creating networks of optical telescopes that have the resolution of a single dish hundreds of kilometres wide.

Two of the studies 1 , 2 were published in Nature on 15 May. The third was described last month in a preprint posted on arXiv 3 , which has not yet been peer reviewed.

Impractical environment

Many of the technical steps for building a quantum internet have been demonstrated in the laboratory over the past decade or so. And researchers have shown that they can produce entangled photons using lasers in direct line of sight of each other, either in separate ground locations or on the ground and in space.

But going from the lab to a city environment is “a different beast”, says Ronald Hanson, a physicist who led the Dutch experiment 3 at the Delft University of Technology. To build a large-scale network, researchers agree that it will probably be necessary to use existing optical-fibre technology. The trouble is, quantum information is fragile and cannot be copied; it is often carried by individual photons, rather than by laser pulses that can be detected and then amplified and emitted again. This limits the entangled photons to travelling a few tens of kilometres before losses make the whole thing impractical. “They also are affected by temperature changes throughout the day — and even by wind, if they’re above ground,” says Northup. “That’s why generating entanglement across an actual city is a big deal.”

The three demonstrations each used different kinds of ‘quantum memory’ device to store a qubit, a physical system such as a photon or atom that can be in one of two states — akin to the ‘1’ or ‘0’ of ordinary computer bits — or in a combination, or ‘quantum superposition’, of the two possibilities.

The quantum internet has arrived (and it hasn’t)

In one of the Nature studies, led by Pan Jian-Wei at the University of Science and Technology of China (USTC) in Hefei, qubits were encoded in the collective states of clouds of rubidium atoms 1 . The qubits’ quantum states can be set using a single photon, or can be read out by ‘tickling’ the atomic cloud to emit a photon. Pan’s team had such quantum memories set up in three separate labs in the Hefei area. Each lab was connected by optical fibres to a central ‘photonic server’ around 10 kilometres away. Any two of these nodes could be put in an entangled state if the photons from the two atom clouds arrived at the server at exactly the same time.

By contrast, Hanson and his team established a link between individual nitrogen atoms embedded in small diamond crystals with qubits encoded in the electron states of the nitrogen and in the nuclear states of nearby carbon atoms 3 . Their optical fibre went from the university in Delft through a tortuous 25-kilometre path across the suburbs of The Hague to reach a second laboratory in the city.

In the US experiment, Mikhail Lukin, a physicist at Harvard University in Cambridge, Massachusetts, and his collaborators also used diamond-based devices, but with silicon atoms instead of nitrogen, making use of the quantum states of both an electron and a silicon nucleus 2 . Single atoms are less efficient than atomic ensembles at emitting photons on demand, but they are more versatile, because they can perform rudimentary quantum computations. “Basically, we entangled two small quantum computers,” says Lukin. The two diamond-based devices were in the same building at Harvard, but to mimic the conditions of a metropolitan network, the researchers used an optical fibre that snaked around the local Boston area. “It crosses the Charles River six times,” Lukin says.

Challenges ahead

The entanglement procedure used by the Chinese and the Dutch teams required photons to arrive at a central server with exquisite timing precision, which was one of the main challenges in the experiments. Lukin’s team used a protocol that does not require such fine-tuning: instead of entangling the qubits by getting them to emit photons, the researchers sent one photon to entangle itself with the silicon atom at the first node. The same photon then went around the fibre-optic loop and came back to graze the second silicon atom, thereby entangling it with the first.

Pan has calculated that at the current pace of advance, by the end of the decade his team should be able to establish entanglement over 1,000 kilometres of optical fibres using ten or so intermediate nodes, with a procedure called entanglement swapping . (At first, such a link would be very slow, creating perhaps one entanglement per second, he adds.) Pan is the leading researcher for a project using the satellite Micius , which demonstrated the first quantum-enabled communications in space, and he says there are plans for a follow-up mission.

“The step has now really been made out of the lab and into the field,” says Hanson. “It doesn’t mean it’s commercially useful yet, but it’s a big step.”

Nature 629 , 734-735 (2024)

doi: https://doi.org/10.1038/d41586-024-01445-2

Knaut, C. M. et al. Nature 629 , 573–578 (2024).

Article   PubMed   Google Scholar  

Liu, J. L. et al. Nature 629 , 579–585 (2024).

Stolk, A. J. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2404.03723 (2024).

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When Online Content Disappears

38% of webpages that existed in 2013 are no longer accessible a decade later, table of contents.

• Webpages from the last decade
• Links on government websites
• Links on news websites
• Reference links on Wikipedia
• Posts on Twitter
• Acknowledgments
• Collection and analysis of Twitter data
• Data collection for World Wide Web websites, government websites and news websites
• Data collection for Wikipedia source links
• Evaluating the status of pages and links
• Definition of links

Pew Research Center conducted the analysis to examine how often online content that once existed becomes inaccessible. One part of the study looks at a representative sample of webpages that existed over the past decade to see how many are still accessible today. For this analysis, we collected a sample of pages from the Common Crawl web repository for each year from 2013 to 2023. We then tried to access those pages to see how many still exist.

A second part of the study looks at the links on existing webpages to see how many of those links are still functional. We did this by collecting a large sample of pages from government websites, news websites and the online encyclopedia Wikipedia .

We identified relevant news domains using data from the audience metrics company comScore and relevant government domains (at multiple levels of government) using data from get.gov , the official administrator for the .gov domain. We collected the news and government pages via Common Crawl and the Wikipedia pages from an archive maintained by the Wikimedia Foundation . For each collection, we identified the links on those pages and followed them to their destination to see what share of those links point to sites that are no longer accessible.

A third part of the study looks at how often individual posts on social media sites are deleted or otherwise removed from public view. We did this by collecting a large sample of public tweets on the social media platform X (then known as Twitter) in real time using the Twitter Streaming API. We then tracked the status of those tweets for a period of three months using the Twitter Search API to monitor how many were still publicly available. Refer to the report methodology for more details.

The internet is an unimaginably vast repository of modern life, with hundreds of billions of indexed webpages. But even as users across the world rely on the web to access books, images, news articles and other resources, this content sometimes disappears from view.

A new Pew Research Center analysis shows just how fleeting online content actually is:

• A quarter of all webpages that existed at one point between 2013 and 2023 are no longer accessible, as of October 2023. In most cases, this is because an individual page was deleted or removed on an otherwise functional website.

• For older content, this trend is even starker. Some 38% of webpages that existed in 2013 are not available today, compared with 8% of pages that existed in 2023.

This “digital decay” occurs in many different online spaces. We examined the links that appear on government and news websites, as well as in the “References” section of Wikipedia pages as of spring 2023. This analysis found that:

• 23% of news webpages contain at least one broken link, as do 21% of webpages from government sites. News sites with a high level of site traffic and those with less are about equally likely to contain broken links. Local-level government webpages (those belonging to city governments) are especially likely to have broken links.
• 54% of Wikipedia pages contain at least one link in their “References” section that points to a page that no longer exists.

To see how digital decay plays out on social media, we also collected a real-time sample of tweets during spring 2023 on the social media platform X (then known as Twitter) and followed them for three months. We found that:

• Nearly one-in-five tweets are no longer publicly visible on the site just months after being posted. In 60% of these cases, the account that originally posted the tweet was made private, suspended or deleted entirely. In the other 40%, the account holder deleted the individual tweet, but the account itself still existed.
• Certain types of tweets tend to go away more often than others. More than 40% of tweets written in Turkish or Arabic are no longer visible on the site within three months of being posted. And tweets from accounts with the default profile settings are especially likely to disappear from public view.

How this report defines inaccessible links and webpages

There are many ways of defining whether something on the internet that used to exist is now inaccessible to people trying to reach it today. For instance, “inaccessible” could mean that:

• The page no longer exists on its host server, or the host server itself no longer exists. Someone visiting this type of page would typically receive a variation on the “404 Not Found” server error instead of the content they were looking for.
• The page address exists but its content has been changed – sometimes dramatically – from what it was originally.
• The page exists but certain users – such as those with blindness or other visual impairments – might find it difficult or impossible to read.

For this report, we focused on the first of these: pages that no longer exist. The other definitions of accessibility are beyond the scope of this research.

Our approach is a straightforward way of measuring whether something online is accessible or not. But even so, there is some ambiguity.

First, there are dozens of status codes indicating a problem that a user might encounter when they try to access a page. Not all of them definitively indicate whether the page is permanently defunct or just temporarily unavailable. Second, for security reasons, many sites actively try to prevent the sort of automated data collection that we used to test our full list of links.

For these reasons, we used the most conservative estimate possible for deciding whether a site was actually accessible or not. We counted pages as inaccessible only if they returned one of nine error codes that definitively indicate that the page and/or its host server no longer exist or have become nonfunctional – regardless of how they are being accessed, and by whom. The full list of error codes that we included in our definition are in the methodology .

Here are some of the findings from our analysis of digital decay in various online spaces.

To conduct this part of our analysis, we collected a random sample of just under 1 million webpages from the archives of Common Crawl , an internet archive service that periodically collects snapshots of the internet as it exists at different points in time. We sampled pages collected by Common Crawl each year from 2013 through 2023 (approximately 90,000 pages per year) and checked to see if those pages still exist today.

We found that 25% of all the pages we collected from 2013 through 2023 were no longer accessible as of October 2023. This figure is the sum of two different types of broken pages: 16% of pages are individually inaccessible but come from an otherwise functional root-level domain; the other 9% are inaccessible because their entire root domain is no longer functional.

Not surprisingly, the older snapshots in our collection had the largest share of inaccessible links. Of the pages collected from the 2013 snapshot, 38% were no longer accessible in 2023. But even for pages collected in the 2021 snapshot, about one-in-five were no longer accessible just two years later.

We sampled around 500,000 pages from government websites using the Common Crawl March/April 2023 snapshot of the internet, including a mix of different levels of government (federal, state, local and others). We found every link on each page and followed a random selection of those links to their destination to see if the pages they refer to still exist.

Across the government websites we sampled, there were 42 million links. The vast majority of those links (86%) were internal, meaning they link to a different page on the same website. An explainer resource on the IRS website that links to other documents or forms on the IRS site would be an example of an internal link.

Around three-quarters of government webpages we sampled contained at least one on-page link. The typical (median) page contains 50 links, but many pages contain far more. A page in the 90th percentile contains 190 links, and a page in the 99th percentile (that is, the top 1% of pages by number of links) has 740 links.

Other facts about government webpage links:

• The vast majority go to secure HTTP pages (and have a URL starting with “https://”).
• 6% go to a static file, like a PDF document.
• 16% now redirect to a different URL than the one they originally pointed to.

When we followed these links, we found that 6% point to pages that are no longer accessible. Similar shares of internal and external links are no longer functional.

Overall, 21% of all the government webpages we examined contained at least one broken link. Across every level of government we looked at, there were broken links on at least 14% of pages; city government pages had the highest rates of broken links.

For this analysis, we sampled 500,000 pages from 2,063 websites classified as “News/Information” by the audience metrics firm comScore. The pages were collected from the Common Crawl March/April 2023 snapshot of the internet.

Across the news sites sampled, this collection contained more than 14 million links pointing to an outside website. 1 Some 94% of these pages contain at least one external-facing link. The median page contains 20 links, and pages in the top 10% by link count have 56 links.

Like government websites, the vast majority of these links go to secure HTTP pages (those with a URL beginning with “https://”). Around 12% of links on these news sites point to a static file, like a PDF document. And 32% of links on news sites redirected to a different URL than the one they originally pointed to – slightly less than the 39% of external links on government sites that redirect.

When we tracked these links to their destination, we found that 5% of all links on news site pages are no longer accessible. And 23% of all the pages we sampled contained at least one broken link.

Broken links are about as prevalent on the most-trafficked news websites as they are on the least-trafficked sites. Some 25% of pages on news websites in the top 20% by site traffic have at least one broken link. That is nearly identical to the 26% of sites in the bottom 20% by site traffic.

For this analysis, we collected a random sample of 50,000 English-language Wikipedia pages and examined the links in their “References” section. The vast majority of these pages (82%) contain at least one reference link – that is, one that directs the reader to a webpage other than Wikipedia itself.

In total, there are just over 1 million reference links across all the pages we collected. The typical page has four reference links.

The analysis indicates that 11% of all references linked on Wikipedia are no longer accessible. On about 2% of source pages containing reference links, every link on the page was broken or otherwise inaccessible, while another 53% of pages contained at least one broken link.

For this analysis, we collected nearly 5 million tweets posted from March 8 to April 27, 2023, on the social media platform X, which at the time was known as Twitter. We did this using Twitter’s Streaming API, collecting 3,000 public tweets every 30 minutes in real time. This provided us with a representative sample of all tweets posted on the platform during that period. We monitored those tweets until June 15, 2023, and checked each day to see if they were still available on the site or not.

At the end of the observation period, we found that 18% of the tweets from our initial collection window were no longer publicly visible on the site . In a majority of cases, this was because the account that originally posted the tweet was made private, suspended or deleted entirely. For the remaining tweets, the account that posted the tweet was still visible on the site, but the individual tweet had been deleted.

Which tweets tend to disappear?

Tweets were especially likely to be deleted or removed over the course of our collection period if they were:

• Written in certain languages. Nearly half of all the Turkish-language tweets we collected – and a slightly smaller share of those written in Arabic – were no longer available at the end of the tracking period.
• Posted by accounts using the site’s default profile settings. More than half of tweets from accounts using the default profile image were no longer available at the end of the tracking period, as were more than a third from accounts with a default bio field. Tweets from these accounts tend to disappear because the entire account has been deleted or made private, as opposed to the individual tweet being deleted.
• Posted by unverified accounts.

We also found that removed or deleted tweets tended to come from newer accounts with relatively few followers and modest activityon the site. On average, tweets that were no longer visible on the site were posted by accounts around eight months younger than those whose tweets stayed on the site.

And when we analyzed the types of tweets that were no longer available, we found that retweets, quote tweets and original tweets did not differ much from the overall average. But replies were relatively unlikely to be removed – just 12% of replies were inaccessible at the end of our monitoring period.

Most tweets that are removed from the site tend to disappear soon after being posted. In addition to looking at how many tweets from our collection were still available at the end of our tracking period, we conducted a survival analysis to see how long these tweets tended to remain available. We found that:

• 1% of tweets are removed within one hour
• 3% within a day
• 10% within a week
• 15% within a month

Put another way: Half of tweets that are eventually removed from the platform are unavailable within the first six days of being posted. And 90% of these tweets are unavailable within 46 days.

Tweets don’t always disappear forever, though. Some 6% of the tweets we collected disappeared and then became available again at a later point. This could be due to an account going private and then returning to public status, or to the account being suspended and later reinstated. Of those “reappeared” tweets, the vast majority (90%) were still accessible on Twitter at the end of the monitoring period.

• For our analysis of news sites, we did not collect or check the functionality of internal-facing on-page links – those that point to another page on the same root domain. ↩

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