Referencing

The IB requires you to use a consistent referencing style throughout your extended essay. At our school, we use Chicago Notes-Bibliography (17th edition). This guide focuses on the sources you are most likely to use, especially those found online.

Referencing properly is not just about avoiding plagiarism. It shows the examiner the quality and breadth of your research. A well-referenced essay builds credibility and demonstrates academic integrity.

How Chicago referencing works

Chicago Notes-Bibliography uses two components:

Footnotes: numbered references at the bottom of each page, inserted using your word processor's footnote tool. These tell the reader exactly where a piece of information came from.
Bibliography: a complete alphabetical list of every source you cited, placed at the end of your essay.

Every footnoted source must appear in the bibliography, and every bibliography entry must have at least one corresponding footnote.

Key differences between footnotes and bibliography entries

The same source looks slightly different in a footnote and in the bibliography:

Author name order. Footnotes: first name then surname. Bibliography: surname then first name.
Punctuation. Footnotes use commas between elements. Bibliography entries use full stops.
Page numbers. Footnotes cite the specific page you used. Bibliography entries give the full page range (for articles).

Shortened footnotes

The first time you cite a source, use the full footnote. Every time after that, use a shortened footnote:

Format: Author Surname, Short Title, page number.

Example:

First citation: 1. Jack Kerouac, The Dharma Bums (New York: Viking Press, 1958), 128.
Second citation: 4. Kerouac, The Dharma Bums, 45.

The 17th edition discourages the use of "ibid." (a Latin abbreviation meaning "in the same place"). Use shortened footnotes instead.

Citing online sources

Most of your sources will come from the internet. The key rule is: cite the source type, not the medium. A journal article found online is still a journal article. A government report downloaded as a PDF is still a report. Always identify what the source actually is before deciding how to format it.

Websites and web pages

Footnote:
1. Author First Name Surname, "Title of Web Page," Name of Website, date, URL.

Bibliography:
Surname, First Name. "Title of Web Page." Name of Website. Date. URL.

Example:

Footnote: 1. Meadhbh Hayden, "My Tips for Swimming in the Irish Sea," SpunOut.ie, February 23, 2021, https://spunout.ie/voices/advice/my-tips-swimming-irish-sea.
Bibliography: Hayden, Meadhbh. "My Tips for Swimming in the Irish Sea." SpunOut.ie. February 23, 2021. https://spunout.ie/voices/advice/my-tips-swimming-irish-sea.

Online journal articles

A DOI (Digital Object Identifier) is a permanent link to an academic source. It looks like https://doi.org/10.1057/ajp.2008.22. Always use a DOI if one is available, as it is more reliable than a URL which can break over time. You will find DOIs on most journal articles.

Footnote:
1. Author First Name Surname, "Title of Article," Journal Title volume, no. issue (Year): page, DOI or URL.

Bibliography:
Surname, First Name. "Title of Article." Journal Title volume, no. issue (Year): page range. DOI or URL.

Example:

Footnote: 1. Andrew Jotischky, "The Christians of Jerusalem, the Holy Sepulchre and the Origins of the First Crusade," Crusades 7, no. 1 (2008): 36, http://eprints.lancs.ac.uk/19762/1/proofs_Crusades_7_03_Jotischky.pdf.
Bibliography: Jotischky, Andrew. "The Christians of Jerusalem, the Holy Sepulchre and the Origins of the First Crusade." Crusades 7, no. 1 (2008): 35–57. http://eprints.lancs.ac.uk/19762/1/proofs_Crusades_7_03_Jotischky.pdf.

Notice that the footnote cites the specific page you referenced, while the bibliography gives the full page range of the article.

Online newspaper articles

Footnote:
1. Author First Name Surname, "Title of Article," Newspaper Title, Month Day, Year, URL.

Bibliography:
Surname, First Name. "Title of Article." Newspaper Title, Month Day, Year. URL.

Blog posts

Footnote:
1. Author First Name Surname, "Title of Post," Title of Blog (blog), date, URL.

Bibliography:
Surname, First Name. "Title of Post." Title of Blog (blog). Date. URL.

YouTube videos

Footnote:
1. Author/Uploader, "Title of Video," Month Day, Year, video, duration, URL.

Bibliography:
Author/Uploader. "Title of Video." Month Day, Year. Video, duration. URL.

Example:

Footnote: 1. Alejandra Ortega, "Grammar: Active and Passive Voice," February 1, 2019, video, 4:22, https://youtu.be/GEP-8lFTKKg.
Bibliography: Ortega, Alejandra. "Grammar: Active and Passive Voice." February 1, 2019. Video, 4:22. https://youtu.be/GEP-8lFTKKg.

Social media posts

Social media posts are typically cited in footnotes only and do not need a bibliography entry unless the post is discussed in detail.

1. Author Name (@handle), "Post text (up to 160 characters)," Platform, Month Day, Year, URL.

Citing books and chapters

Books

Footnote:
1. First Name Surname, Title of Book (Place: Publisher, Year), page.

Bibliography:
Surname, First Name. Title of Book. Place: Publisher, Year.

Example:

Footnote: 1. Jack Kerouac, The Dharma Bums (New York: Viking Press, 1958), 128.
Bibliography: Kerouac, Jack. The Dharma Bums. New York: Viking Press, 1958.

Multiple authors

2–3 authors: list all names in the footnote and bibliography.
4 or more authors: in the footnote, give the first author followed by "et al." (Latin for "and others"). In the bibliography, list all authors.

Book chapters

Footnote:
1. First Name Surname, "Chapter Title," in Title of Book, ed. Editor Name (Place: Publisher, Year), page.

Bibliography:
Surname, First Name. "Chapter Title." In Title of Book, edited by Editor Name, page range. Place: Publisher, Year.

Citing AI-generated content

If you use AI tools like ChatGPT during your research, you must cite them. Be aware that the IB has strict rules about how AI may be used in the extended essay. Always check with your supervisor before relying on AI-generated content.

Footnote:
1. ChatGPT, response to "Your prompt here," OpenAI, Month Day, Year.

Bibliography:
ChatGPT. Response to "Your prompt here." ChatGPT-4, Month Day, Year. URL (if available).

For AI-generated images, use a caption format:

Fig. 1. Image generated by DALL-E 3, Month Day, Year, from the prompt "your prompt."

Access dates

Access dates are not required for formally published sources with a clear publication date.
Access dates are required when a source has no publication date. Format: "accessed Month Day, Year."
Tip: When in doubt, include the access date. It can only help.

Handling missing information

Online sources often have incomplete information. Here is how to handle the most common gaps:

No author

First, check whether an organisation can serve as the author (e.g. BBC, World Health Organization). If not, begin with the title of the work.

1. "Illinois Governor Wants to 'Fumigate' State's Government," CNN, January 30, 2009, URL.

No date

Omit the date and include an access date instead:

1. "Conservation," Los Angeles County Museum of Art, accessed March 10, 2020, URL.

No page numbers

Simply omit the page number. If you are quoting directly, you may include a section heading or paragraph number to help the reader find the passage. Never count pages or paragraphs yourself.

Common mistakes to avoid

Superscript placement. The small raised footnote number goes after the punctuation mark (full stop, comma), not before.
Repeating full footnotes. After the first citation, always use a shortened footnote. Repeating the full version wastes your word count.
Mixing up footnote and bibliography formatting. Remember: footnotes use commas and first-name-first; bibliography uses full stops and surname-first.
Footnote-bibliography mismatch. Every source in your footnotes must appear in the bibliography, and vice versa. Cross-check before you submit.
Treating everything as a "website." A journal article found online is a journal article. A report downloaded as a PDF is a report. Identify the source type first.
Missing URLs or DOIs for online sources. If you accessed it online, include the link.
Inconsistent date formatting. Chicago uses Month Day, Year throughout (e.g. "January 30, 2024"). Do not switch between formats.
Using "ibid." everywhere. The 17th edition discourages this. Use shortened footnotes instead.

Tips for success

Cite as you write. Insert footnotes as you draft. Do not leave referencing until the end.
Keep a running bibliography. Maintain your bibliography alongside your research, not after you finish writing.
Always check for a DOI on journal articles before defaulting to a URL.
Cross-reference your footnotes against your bibliography as a final check before submission.
Use your word processor's built-in footnote tool. Never type footnote numbers manually.