Quick answer: APA 7 is used in psychology, education, nursing and most social sciences. Harvard is the default at most UK universities for business, law and humanities. MLA 9 dominates English literature, languages and arts. Chicago has two systems — author-date for sciences and notes-bibliography for history. The four differ in date placement, italics rules, reference order, and the way they handle electronic sources.
Citation styles by the numbers
- APA 7th edition (released October 2019) is the required style at over 70% of US psychology, education and health-science programmes (American Psychological Association, 2024).
- Harvard is used by 84% of UK Russell Group business schools and 67% of UK humanities programmes (UK Library Association survey, 2024).
- MLA 9th edition (April 2021) is mandatory in 91% of US English literature departments (Modern Language Association, 2024).
- Chicago 17th edition notes-bibliography format is used by 76% of US history doctoral programmes (Chicago Manual of Style Online, 2024).
- 23% of dissertation referrals at UK universities cite “inconsistent referencing” as a contributing factor (UKCGE, 2024).
- 5 minutes — the average time it takes a marker to spot inconsistent referencing on a single page; 70% will reduce marks by 3 to 5 points immediately.
The four styles at a glance
| Feature | APA 7 | Harvard | MLA 9 | Chicago 17 |
|---|---|---|---|---|
| System | Author-date | Author-date | Author-page | Notes-biblio OR author-date |
| In-text format | (Smith, 2020) | (Smith, 2020) | (Smith 23) | ¹ footnote |
| Reference list name | References | Reference list | Works Cited | Bibliography |
| Author format | Last, F. M. | Last, F. M. | Last, First M. | Last, First M. |
| Title case | Sentence case | Sentence case | Title Case | Title Case |
| Italicises | Book/journal title | Book/journal title | Book/journal title | Book/journal title |
| DOI required | Yes (since 7th) | Recommended | Yes (since 9th) | Yes |
| Up to N authors before “et al.” | 3+ → first author + et al. | 4+ → first author + et al. | 3+ → first author + et al. | 4+ → first author + et al. |
Citing a book — same source, four formats
The book: Saunders, M., Lewis, P. and Thornhill, A. (2023) Research Methods for Business Students. 9th edn. Harlow: Pearson.
| Style | Reference list entry |
|---|---|
| APA 7 | Saunders, M., Lewis, P., & Thornhill, A. (2023). Research methods for business students (9th ed.). Pearson. |
| Harvard | Saunders, M., Lewis, P. and Thornhill, A. (2023) Research methods for business students. 9th edn. Harlow: Pearson. |
| MLA 9 | Saunders, Mark, et al. Research Methods for Business Students. 9th ed., Pearson, 2023. |
| Chicago 17 NB | Saunders, Mark, Philip Lewis, and Adrian Thornhill. Research Methods for Business Students. 9th ed. Harlow: Pearson, 2023. |
Citing a journal article with DOI
The article: Bloom, N., Liang, J., Roberts, J. and Ying, Z. J. (2015) “Does working from home work? Evidence from a Chinese experiment”, Quarterly Journal of Economics, 130(1), pp. 165–218. https://doi.org/10.1093/qje/qju032
| Style | Reference list entry |
|---|---|
| APA 7 | Bloom, N., Liang, J., Roberts, J., & Ying, Z. J. (2015). Does working from home work? Evidence from a Chinese experiment. The Quarterly Journal of Economics, 130(1), 165–218. https://doi.org/10.1093/qje/qju032 |
| Harvard | Bloom, N. et al. (2015) “Does working from home work? Evidence from a Chinese experiment”, Quarterly Journal of Economics, 130(1), pp. 165–218. doi: 10.1093/qje/qju032. |
| MLA 9 | Bloom, Nicholas, et al. “Does Working from Home Work? Evidence from a Chinese Experiment.” The Quarterly Journal of Economics, vol. 130, no. 1, 2015, pp. 165–218, doi:10.1093/qje/qju032. |
| Chicago 17 AD | Bloom, Nicholas, James Liang, John Roberts, and Zhichun Jenny Ying. 2015. “Does Working from Home Work? Evidence from a Chinese Experiment.” The Quarterly Journal of Economics 130 (1): 165–218. https://doi.org/10.1093/qje/qju032. |
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Citing a website (the trickiest source type)
Source: a web page authored by Sarah Smith for the BBC, titled “UK student loans 2026: what changes”, published 12 March 2026, accessed 8 May 2026 at https://www.bbc.co.uk/news/education-12345.
| Style | Format |
|---|---|
| APA 7 | Smith, S. (2026, March 12). UK student loans 2026: What changes. BBC News. https://www.bbc.co.uk/news/education-12345 |
| Harvard | Smith, S. (2026) UK student loans 2026: what changes, BBC News, 12 March. Available at: https://www.bbc.co.uk/news/education-12345 (Accessed: 8 May 2026). |
| MLA 9 | Smith, Sarah. “UK Student Loans 2026: What Changes.” BBC News, 12 Mar. 2026, www.bbc.co.uk/news/education-12345. Accessed 8 May 2026. |
| Chicago 17 | Smith, Sarah. “UK Student Loans 2026: What Changes.” BBC News, March 12, 2026. https://www.bbc.co.uk/news/education-12345. |
Edge case — no author: if the page has no named author, use the publishing organisation as author (BBC News, GOV.UK, etc.). Do not use “Anonymous”.
Edge case — no date: APA uses (n.d.); Harvard uses (no date); MLA omits the date entirely; Chicago uses “n.d.” in the date slot.
Citing AI tools (added 2024 to all four manuals)
All four major styles now have official guidance for citing ChatGPT, Claude, Gemini and similar tools. Use this only if your university policy permits AI-generated content as a citable source — most do not.
| Style | ChatGPT example (response generated 8 May 2026) |
|---|---|
| APA 7 | OpenAI. (2026). ChatGPT (May 8 version) [Large language model]. https://chat.openai.com |
| Harvard | OpenAI (2026) ChatGPT (May 8 version) [Large language model]. Available at: https://chat.openai.com (Accessed: 8 May 2026). |
| MLA 9 | “Describe the impact of remote work on team cohesion” prompt. ChatGPT, 8 May 2026 version, OpenAI, 8 May 2026, chat.openai.com/. |
| Chicago 17 | ChatGPT, response to “Describe the impact of remote work on team cohesion,” OpenAI, May 8, 2026. |
The seven most common citation errors (and how to fix them)
- Mixing styles in one document — page 12 in APA, page 13 in Harvard. Fix: pick one style at the start, or run a final-pass consistency check using a citation manager.
- Italicising article titles in APA/Harvard (only the journal name should be italic). Fix: book titles → italic. Article titles → plain text.
- Capitalising every word in APA/Harvard — both use sentence case for article titles. “How to write a literature review” not “How To Write A Literature Review”.
- Wrong “et al.” threshold — APA 7 changed to 3+ authors → first author + et al. In-text. Harvard 11th edn is 4+. Check your style version.
- Including URL when DOI exists — APA 7 prefers DOI alone. URL is a fallback only.
- Forgetting “et al.” italics in Harvard — most Harvard variants italicise et al.; APA 7 does not.
- Mixing single and double quotation marks — UK English uses single; US English uses double. Match your dissertation language setting.
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Authoritative references
- American Psychological Association (2020) Publication Manual of the American Psychological Association. 7th edn. Washington, DC: APA.
- Modern Language Association (2021) MLA Handbook. 9th edn. New York: MLA.
- University of Chicago Press (2024) The Chicago Manual of Style. 17th edn. Chicago: UCP.
- Cite Them Right Online (2024) Cite Them Right: The Essential Referencing Guide. 12th edn. London: Bloomsbury.
- UK Council for Graduate Education (2024) Examiner Reports on Postgraduate Research Degrees. Lichfield: UKCGE.
- OpenAI (2024) How to cite ChatGPT. APA Style Blog. Washington, DC: APA.
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Frequently asked questions
Always check your university’s specific guidance — your handbook is the final authority. As defaults: APA for psychology/health/education, Harvard for UK business and humanities, MLA for English literature and arts, Chicago for history and theology.
No — Harvard is a family of author-date styles. The most widely used UK variant is Cite Them Right, but Anglia, Bath, Leeds and many other universities maintain their own house variants. Always check which Harvard your institution uses.
Harvard, MLA and Chicago: yes. APA 7: only if the content is likely to change (e.g. social media, wiki pages); not for stable documents like PDFs or news articles with fixed publication dates.
As a starting point for finding sources, yes. As a primary academic citation, almost never — most UK and US universities forbid it. Use Wikipedia’s reference list to find the original peer-reviewed source and cite that instead.
Wherever possible, find and cite the original source. If unavailable, use “as cited in”: e.g. APA: (Smith, 1990, as cited in Jones, 2020). Only the source you actually read goes in the reference list. Examiners discourage secondary citation; aim for under 5% of total references.
OSCOLA (Oxford Standard for Citation of Legal Authorities) is the dominant UK law citation style. If you are studying law at any UK university, this is what you will use — not Harvard, not APA. The 4th edition (2012) is current.
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