What is a Citation?
A citation tells your reader where an idea, quotation, fact or piece of data came from. In academic writing it has two parts: a short marker in the text, and a full entry in the reference list or bibliography that lets the reader find the source.
Why Citations Matter
- Credit: it acknowledges other people's work, which is the core of academic integrity.
- Evidence: it shows that your claims rest on research, not opinion.
- Checking: it lets readers verify your sources and read further.
When Do You Need a Citation?
- Direct quotations, always with page numbers where the style asks for them.
- Paraphrases and summaries of someone else's ideas.
- Facts, statistics, data, images and tables taken from a source.
- Not usually needed for common knowledge, such as "Paris is the capital of France", but if in doubt, cite.
In-Text Citation and Full Reference
- In-text citation: a short marker, such as (Johnson, 2023, p. 45), a number [3], or a footnote.
- Full reference: author, year, title, source (journal, publisher or website) and, for online sources, a DOI or URL.
The Same Source in Five Styles
An invented journal article, cited in text:
- APA: (Johnson, 2023, p. 45)
- MLA: (Johnson 45)
- Chicago author-date: (Johnson 2023, 45)
- Harvard: (Johnson, 2023, p. 45) in the common Cite Them Right version, the same as APA in the text; the reference lists differ
- IEEE and Vancouver: a number matching a numbered reference list: [1] in IEEE, (1) or a superscript in Vancouver.
What is a DOI in a Citation?
A DOI (Digital Object Identifier) is a permanent ID for a paper, such as 10.1000/xyz123, that keeps working even if the publisher's website changes. APA and many other styles ask you to include it, written as a link: https://doi.org/10.1000/xyz123.
Making Citations Easier
A citation generator or reference manager formats entries for you, but check each one. In Papero you can look a paper up by DOI, PMID, arXiv ID or ISBN through OpenAlex and Crossref and cite it as you write, in nine styles from APA to Vancouver; the reference list is built from those papers, never made up.
Full guide: How to Cite a Book: APA 7, MLA 9 and Chicago 18 Examples
Free tool: DOI to citation generator
Free tool: Reference checker and citation checker