Citing Sources: What, When, and How Often to Cite

One of the most common questions about citing sources is: how often must I cite? Many students think it’s acceptable to cite a source once at the end of a paragraph, but to make clear where your information came from, you need to cite much more often than that.

You need to cite every time you’ve used words, ideas, or images from a source. If it didn’t come from your own head, show where it did come from. And you need to place the citation with the source material either in the sentence itself or in parenthesis at the end of it.

Citing Sources: What to Cite

There are only two things that don’t require citation. They are:

- Common knowledge. If it’s a fact the average person could be expected to know, or if you could easily find the same information in numerous reference materials, you don’t need a citation. For example, if you write that the American Declaration of Independence was signed in 1776, you wouldn’t need to cite a source.

- Your own experiences, observations, memories, thoughts, and opinions. If you’re writing from knowledge that you had already before you did any research, you don’t need to cite a source. It’s assumed that anything in your paper that isn’t attributed to a source comes from you.

Citing Sources: When to Cite

Remember that the purpose of citations is to make clear to readers which material in your essay comes from a source and which is your own thoughts. So you need to cite every time to use material from your research.

You should place a citation in any sentence in which you use words, thoughts, facts, or opinions that you learned from a source. This is true whether you use the exact words of the source or put the information into your own words.

If you’ve used a lot of research in your paper, this may mean that every sentence will contain a citation. That’s a good thing: it shows that you did extensive research and can back up your points. To keep the citations from becoming repetitious, you can very them: sometimes putting the citation directly into the sentence (“According to…”) other times using parenthetical citations. (See the articles on how APA and MLA work).

Citing Sources: How Often to Cite

Whenever you use a source, you should let readers know that as early as possible and tell them what the source is.

Because citations are designed to show readers which material came from a source and which from you, it isn’t sufficient to cite once at the end of a paragraph. You need to include a citation for every piece of borrowed information. But you don’t always have to do it in parenthesis. If you have a long passage of information paraphrased from a single source, you can introduce it with a signal phrase (such as “According to…”) and place a parenthetical citation at the end.

MLA Citation Examples

When the advent of large publishing firms in the twentieth century made it possible to offer authors everything from editing to distribution under one roof, self-publishing fell out of favor (DuHadaway par. 2). While the option for an author to publish his or her own work has always been available through book manufacturers and subsidy publishers, the resulting books have been looked down on by booksellers and reviewers as inferior products (Ross 1). Tom and Marilyn Ross quote one reviewer, “Self-published books come in four at a time, and when I see the imprint, I throw them immediately in the wastebasket. I wouldn’t even give them away” (44). A further difficulty is created by the fact that self-publishing outfits offer bookstores only a twenty-five to thirty percent discount as opposed to the usual forty percent and don’t allow the return of books (Ross 35).

You’ll notice in this paragraph that every sentence contains information from a source, one from DuHadaway and the other three from Ross. Do you see how easy it is to identify which information came from each one? You’ll also notice that the frequent citations don’t interfere at all with reading the paragraph smoothly. In one case, the authors are named in the sentence; in the other cases they’re in the parenthesis. But either way, you can clearly see which information came from which sources.

NOTE: You don’t need to put parenthesis around a signal statement. Students sometimes mistakenly think that because they are citing their source, parenthesis are necessary. Use the parenthesis only if you’re adding the citation to the end of the sentence, not if it’s part of the sentence.

Use the MLA and APA style guides to be sure you’re including the correct information in the your citations. It will be very brief, such as author and page number or year. You never want to include full bibliographic information in the body of your essay. Save the publication information for the bibliography at the end of your paper.

I hope this answers all your questions about citing sources. You can find specific instructions for citing in APA and MLA style on the Research Paper Help page.

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