# Cite articles or book where I first found the result?

I'm writing up a paper and I'm not sure how to cite a few things. It concerns a conjecture made by Quillen. Some work has been done showing it's true in some cases, false in others. These results I found in a book that had a chapter about the conjecture; of course, the book gave all the references. In the background of my paper, I want to briefly sum up these results. My question is, should I cite the articles, the book, or both? I wasn't sure what the etiquette/rules are in this situation.

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Why not cite the book and say that the relevant chapter includes primary references? –  Andres Caicedo May 15 '11 at 4:06
When you cite, you are not just providing useful information to the reader. You are also giving credit where it is due. And since people's careers and lives depend at least somewhat if not a lot on getting this credit, I encourage you to give it. So please try to list all of the primary sources in the bibliography, as well as the book. In the body of the paper, you cite the papers in the appropriate places. If you don't specifically state or use the result from a paper that deserves to be cited, just say "See also [1,3-7,15] for other related work." –  Deane Yang May 15 '11 at 4:16
I strongly agree with what Deane says. Mathematicians tend to be stingier with citations than other scientists (which causes many headaches when dealing with promotion cases, etc.). Don't make this even worse. If someone clearly did related work, cite their paper and not the secondary literature! –  Andy Putman May 15 '11 at 4:45
While I take Deane and Andy's point: since I am extremely reluctant to cite things I haven't read, and since sometimes the original sources have an incomplete presentation of what I wish to reference, I sometimes refer people to one of the standard texts. However, I do try to give attribution to the relevant people. –  Yemon Choi May 15 '11 at 5:33
I try to cite only references I have read. In my opinion, citing a reference implies that you referred to it when you wrote your paper, that is, that you read it. Try your best to read the references that the book refers to, and then cite them as well as the book. –  Joel Reyes Noche May 15 '11 at 6:18

When in doubt, cite. Cite the paper, cite the book, and explain what is it where. You've already done the hard part, so let the reader benefit from your work. It does you no harm, and is helpful for your readers.

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I feel compelled to repeat and stress my answer: Cite generously and often.

Some have expressed the principle of citing only references that they have read themselves. This seems attractive as some kind of ethical principle, but I believe it is misguided. It would make sense only if most people in the math community assume this when they see references in a paper. But, as far as I can tell, there is no such common view. References, like everything else in the paper, are there to communicate knowledge, as completely as possible, either by stating the knowledge direcctly or by citing references. When you cite a reference, you are telling the audience that you know about it and not that you have read it.

To me, what is far more important than such a principle is serving the good of the subject and community. Citing generously not only papers you have read yourself but papers you know about that are related to your own paper has the following positive benefits:

• As others have mentioned, it saves people the trouble of having to find things by looking up other secondary references first. Even if the primary source is now known to everybody, many of us want to know who and which paper. Even if the theorem no longer has a name attached to it, say whose theorem it is and where the primary reference is. Why make us chase it down?

• It helps promote and demonstrate the vitality of the topic of the paper. As Andy Putnam mentioned, too many mathematicians are stingy with their citations, making our citation numbers much lower than other fields. This has hampered our ability to compete for positions and funding relative to other fields, because funding agencies and deans have doubts about how many people know or care about our work. So if you know about a paper and believe it to be good work (perhaps based on either other papers you have read or recommendations by other mathematicians you trust), you should cite and help promote it, even if you have not read it yourself.

• Citing contemporaries who have done good work on the same topic helps their reputation and careers. You want them to do the same for your work, so you need to do it, too. Imagine if you were the first to prove a theorem but everybody started citing only the paper that had a much simpler proof.

Let me also give a concrete example: Nash's original paper on isometric embedding is extremely difficult to understand, and, as far as I can tell, almost no one has ever read it. Luckily, people such as Moser and Sergeraert figured out much simpler proofs of the $C^\infty$ theorem, and that's what most of us read and learn. More recently, Gunther found a way to reproduce the full strength of Nash's original theorem using an extremely simple argument. So I have never read Nash's original proof. I think, however, it would be absurd for me not to cite Nash's original paper just because I haven't read it.

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This attitude has a downside, namely it leads to proliferation of references to papers which have gaps, errors, are incomplete etc. I don't want to use specific names, but it certainly happens that a widely cited paper has gaps in the proofs or is faulty in some way, which those citing it may not be aware of (because they haven't read it and, well, if so many people have cited it before, it "has" to be correct...). –  Michal Kotowski May 15 '11 at 20:56
@Deane: I do not disagree with you. However, one of my concerns is the tendency of some people to cite references without first making sure that the reference exists. For example, say that a paper was published in volume 19 of some journal. Because of a typo, the citation to it states that it was in volume 18. Readers unfamiliar with the paper (because they haven't read it) just copy the citation to volume 18. This type of error is common in the mathematics education literature. My suggestion is to read the paper (not necessarily completely understand it) just to make sure it exists. –  Joel Reyes Noche May 16 '11 at 1:08
In response to some of the objections to what I wrote, I can only agree that it is possible to cite too much and too carelessly. You do want to try to cite only papers that you honestly believe are significant and probably correct. But be generous in citing papers that meet your own personal standards for this. Try to cite primary sources as well as your preferred secondary sources. And the consequences are not so bad, if you sometimes cite a paper, whether based on your own reading of it or by endorsements by colleagues you respect, that turns out to be incorrect. –  Deane Yang May 16 '11 at 1:58

A citation should make reader's job easier! A textbook with the best exposition, or a survey with all the relevant references (if it exists) is a preferred choice, especially where the original sources are obscure, hard to locate, and/or read. So I would write, "by a theorem of Perelman (see e.g. [Morgan-Tian, Theorem 1.2.3])".

Speaking about promotion, by the time the stuff that made it into textbooks, this is (usually) no longer an issue, and in many cases the person responsible for the original result may have achieved a god-like status. Then it is common to even omit the author's name, let alone give a reference to the original source, e.g. people say "by the s-cobordism theorem".

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