Guide to Citations and References


This guide is part of my Advice for Students.

Read This First

This guide is intended for students who are new to using citations and references, or need to refresh their memory. Students entering college or graduate school are sometimes unfamiliar with these concepts, but they absolutely must know this information. If you are a student, your work will be subject to the same standards (which Penn State refers to as academic integrity) regardless of whether you're aware of them.

I've written this guide with a perspective that I call citation positive: I focus on the value that citations add to a writer's work, rather than adopting a stern or punitive tone. Citations contribute to the meaning and significance of a manuscript, and a writer should feel positive motivation to use them rather than using them grudgingly. However, this positivity shouldn't be mistaken for optionality. It's important to remember that the absence of appropriate citations or abuse of citations is plagiarism, which can have serious consequences.

This guide covers the basic concepts of citations and references, rather than committing to a style guide that specifies how they should look. I've linked to some style guides as examples.

Finally, if you find this guide useful then please email me (see "Contacting Me" instructions) or let me know on Twitter.

The Guide


Tall buildings and haze from a nearby hilltop
Central Hong Kong from Victoria Peak.

Citations and References Give Value to Your Work

It's rare for scholarly work to happen in isolation. On extraordinary occasions people produce stunning results all by themselves, but researchers tend to be more productive when they review existing work and then build upon it.

How do you situate your manuscript, demonstrating that (1) you've built upon others' work and (2) you haven't tried (perhaps vainly) to reinvent the wheel? By popular agreement, researchers seek out related work from the research community and cite what they find. Sometimes researchers cite to show that they built upon others' work, and sometimes they cite to compare their work to others'. Either way, giving credit to others lends significance to your work.

Citations give value to your manuscript, which becomes integrated with the literature on the topic you've chosen to write about. Ideally you want lots of integration, with citations to lots of relevant work. You want readers to see that you've thoroughly reviewed others' contributions to a topic, building a solid foundation for your own contributions.

Key Terms

Here are some key terms. I'll explain most of them in greater detail below.

A source is something created by someone else that provides you with information. In academia often this is a scholarly paper, but it also might be a video, a popular news article, or an interview.

A citation is a formal indication in your writing that you borrowed an idea from others' work. It appears near the description of the borrowed idea, often at the beginning of it or just after it. It tends to be brief, consisting of just enough information to connect it with a reference, which appears elsewhere in the manuscript. A citation always connects with a reference in your manuscript.

A reference is a detailed identification of a source that you borrowed ideas from. If you are using citations, then a reference only appears in your manuscript when at least one citation connects with it.

Be aware that citations and references are sometimes together referred to as simply "citations" or "references". For example, in this guide I sometimes refer to them collectively as "citations". However, both citations and references must appear in a scholarly paper. One is incomplete without the other.

References or Works Cited is a section of a manuscript, typically at the end, that lists cited sources.

A bibliography is similar to a References or Works Cited section, except it's used when citations don't appear in the document. (By default, assume that you should use citations and that you shouldn't use a bibliography.)

A quote or quotation is text that you copy or transcribe verbatim (i.e., word-for-word) from a source. Writers use double quote marks or indented margins to distinguish quotations from their own original work. A quotation is incomplete without a citation to indicate where the text is originally from.

A paraphrase is a restatement of others' ideas using your own words. It shouldn't be set apart with double quote marks or indented margins, but it's still incomplete without a citation.

A style guide is a set of instructions for how to assemble a manuscript and write it well. The Modern Language Association's Handbook is an example, and my Guide for Scholarly Writing has some style guide content. Your instructor or a publication venue many point you to a style guide containing instructions for the required format for citations and references.

Finally, a citation manager is a software program that keeps track of your references and automatically generates your citations and your reference list. Citation managers make citations and references easy to work with(!), as I explain in a section below.


Sunset over a city from a historic monument
Sunset over Athens from Lycabettus Hill.

What Style Are You Using?

There is no universal agreement for what citations and references should look like, but there are several well-known standards. If your publication venue or your instructor doesn't give you a standard to follow, look at publications in the same venue or other manuscripts about similar topics and follow the style that they use.

I've placed examples below in boxes, and I've emboldened citations in them to point out exactly where they are. Note that the parentheses or square brackets are part of a citation. In an actual manuscript there would be no boxes or bold text, although italics are used as shown. Sentences would be integrated with normal prose, and references would appear in a list at the end of the manuscript with a heading "References" or "Works Cited".

MLA is one example of a popular style. MLA's citations look like this:

A prior study found a correlation between birth year and favorite color (Gao, 2019).

Sometimes a writer names the authors in the sentence, and the parentheses only contain the year:

Gao (2019) found a correlation between birth year and favorite color.

MLA requires the references to appear in a list at the end of the manuscript, in alphabetical order. A typical entry in an MLA reference list looks like this:

Gao, Naomi. "The Significance of Color Preference." Psychology in Aesthetics, vol. 11, no. 4, 2019, pp. 61-89.

You can find more information about using MLA’s citation and reference style on their website. Note that there are many different types of sources (e.g., journal articles, magazine articles, TV shows, personal interviews, etc.) and there are distinct reference formats for most of them.

Some citation styles use numbers in square brackets. IEEE is an example:

A prior study found a correlation between birth year and favorite color [5].

References are numbered by the order they appear in the manuscript, and they and formatted according to IEEE's specifications:

[5] N. Gao, "The Significance of Color Preference," Psychology in Aesthetics, vol. 11, no. 4, pp. 61-89, 2019.

You may encounter citation styles that use superscripts as citations and footnotes or endnotes to individually contain references, such as the Chicago style. Other styles exist. In all cases, carefully mind the details, including punctuation and spacing.

Many websites provide instructions for how to use popular citation styles, and some are more approachable than the style guides themselves. If you're confused about a style, search around for more input.


Italian city skyline from a nearby hillside
Florence, with Brunelleschi's Dome at center, as seen from Fiesole.

Use a Citation Manager

It's a lot of work to manually keep track of citations and references. Instead, use a citation manager like Zotero (free for anyone) or EndNote (free for students at certain universities). Citation managers allow you to import information about sources automatically or manually, and they can generate citations and references for you on demand. You still have to find sources and know when to cite them, but all of the bookeeping and formatting is done for you. If you keep working in a certain area of research, over time you can build up a reference library using your citation manager, and preparing manuscripts will become progressively easier.

Zotero and EndNote both feature web browser plugins that let you add sources to your library as you find them online. Keep in mind that the websites that host your sources may not provide enough information for your citation manager to create a proper entry in your reference list, or some of it might be incorrect. Double-check the imported reference information for reasonableness and completeness.

Both Zotero and EndNote provide plugins to integrate with Microsoft Word, and you can use either citation manager with LaTeX.

You may see BibTeX mentioned in citation managers or in digital libraries. It's a format for specifying information for sources.

Quotations, Long ("Block") Quotations, and Paraphrases Are All Different

If you repeat verbatim more than a few words in sequence from a source, you've produced a quotation of the source, and it's necessary to use quotation marks. If you reproduce more than a sentence, it's appropriate to format the quotation as long quotation or a block quotation; check your style guide for instructions.

If a citation accompanies text that doesn't contain quote marks or long quotation formatting, the reader assumes you've paraphrased. Ensure that assumption is correct.

Citations and Grammar

Some style guides optionally permit citations to serve as nouns in a sentence:

(Wyatt, 2019) was a detailed study of the Loch Ness Monster that concluded it was an amphibian.

I prefer that students avoid using citations as nouns. I explain this in detail in my Guide for Scholarly Writing.

What If I Overdo It?

Sometimes students wonder if including too many citations will make them look unprofessional or obsessive. If you're using citations properly, don't be concerned about having too many.

Within the context of a graded assignment, it is unlikely you will lose points for including too many citations. Your instructor will note your enthusiasm for following the rules of good writing. I have never deducted points for over-citing, but I have deducted points for malformed or missing citations.

If you're preparing a paper to be submitted for publication, a senior colleague (generally your advisor) can help you determine if your citations are excessive. You should give them a draft with all your citations, and let them decide.


Catalan city skyline from a hillside, with a statue of a person at right, and sunset in the sky
Barcelona from Montjuïc.

What About Public Domain Materials?

Students occasionally think that they do not have to cite public domain materials, on the basis that they are free for anyone to use. However, public domain status is irrelevant: you must cite all materials that you borrow from, regardless of their protection status.

What About Citing and Referencing in Presentation Slides?

There are few (if any) conventions for citing and referencing in presentation slides, but I recommend that students include footnotes in their slides to specify sources when they borrow ideas, text, or images from them. This includes clip art and incidental illustrations.

An Important Warning

Depending on the severity of the infraction, plagiarism can result in a poor grade on an assignment, an automatic failing grade on a course, or ejection from a degree program.

Note that accidental plagiarism is still plagiarism, and a student who is completely unaware of the concept of plagiarism still faces consequences if they plagiarize.

Your Next Steps

If you're preparing a manuscript, your next step is to determine the appropriate citation format. It might or might not be one of the citation formats I mention in this guide.

Also, if you found this guide useful, you might want to check out my Guide for Scholarly Writing.

What's the Purpose of the Pictures in This Guide?

I added them to break up the text; all of them are mine. I am a photographer in my spare time.

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Glittering city skyline at dusk, across a harbor, with boats in the foreground
Doha's city center from across the harbor.