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I have read that references in scientific papers should be no more than 2-3 years old, since such fields move fast, and no more than 10 years for arts or related fields:

A good rule of thumb is to use sources published in the past 10 years for research in the arts, humanities, literature, history, etc.

For faster-paced fields, sources published in the past 2-3 years is a good benchmark since these sources are more current and reflect the newest discoveries, theories, processes, or best practices.

However, I believe that's subjective, so how old is it for a reference to be "too old" to cite?

Nat
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Muizz Mahdy
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    There is no "too old to cite". I've actually referenced some of Adolf Fick's and Einstein's original papers in my dissertation. (And they were such fun to read!) Also, that references need to have a certain age is nonsense. Where did you read this? –  Apr 05 '19 at 11:54
  • Here: http://libanswers.snhu.edu/faq/215024 – Muizz Mahdy Apr 05 '19 at 12:01
  • "For faster-paced fields, sources published in the past 2-3 years is a good benchmark since these sources are more current and reflect the newest discoveries, theories, processes, or best practices." – Muizz Mahdy Apr 05 '19 at 12:01
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    @Roland strictly speaking you are right: as written the OP states that a publication must be older than 2 years before you can cite it. However, given the content of the question I suspect that the OP intended to say that a publication must be younger than 2 years. – Maarten Buis Apr 05 '19 at 12:01
  • I'm not quite sure whether the author of that page meant at least 2 years or within 2 years – Muizz Mahdy Apr 05 '19 at 12:03
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    No study is too old to cite, but not all studies "age well". Especially in fast paced discipline studies can easily be obsolete. However, this does not mean that all older studies in those disciplines become obsolete, just that many do. You can and should use those non-obsolete older ones. – Maarten Buis Apr 05 '19 at 12:07
  • Understood, thank you. Write that into an answer so I could accept it – Muizz Mahdy Apr 05 '19 at 12:13
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    If you are still allowed to reference Plato, that's more than 10 years... – Solar Mike Apr 05 '19 at 12:57
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    I notice the web page you cited says "A good rule of thumb is" and "is a good benchmark", which is a lot softer than your wording suggests, especially in trying to pin-point the exact suggested constraints. Also, the librarian's answer clearly seems to be designed for undergraduate research papers and projects, and a quick check shows the university serves almost entirely undergraduates. Finally, a look at the "Related FAQs" titles on the right side shows the kinds of things (allowing for a 40 year gap) covered in my required freshman English composition course. – Dave L Renfro Apr 05 '19 at 13:19
  • Can you put the link into the question? – Ingo Apr 05 '19 at 13:28
  • Related if not duplicate: How can I tell if a paper is too old to be a reference for my research? – Wrzlprmft Apr 05 '19 at 14:43
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    Maxwell's equations, Kepler's laws of planetary motion, Mass–energy equivalence? Nope, they're all much too old to be used in any serious research paper! – Eric Duminil Apr 05 '19 at 15:51
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    One horrible pattern I have observed is when people cite current-year papers for centuries old obvious common knowledge. It comes across as blatant citation count inflation, so don't do it. – Display Name Apr 05 '19 at 16:06
  • So - if someone writes a paper explaining why Noahs flood never happened; are you saying they're not allowed to reference the bible? Seems a little harsh to me. – UKMonkey Apr 05 '19 at 19:14
  • The oldest paper I cited in my PhD thesis (in pure mathematics) is an article of Schur of 1890. Of course, in mathematics older papers remain true and relevant, while in other fields it can be different. – Daniel Robert-Nicoud Apr 05 '19 at 20:38
  • @Daniel Robert-Nicoud: I was curious about my PhD thesis, but I stopped counting after 18 entries from the 1800s, the last of which by Dini (i.e. in the D's). Earliest I saw was this 1806 paper by Ampère, but I was only searching for appearances of "18", so there might be a 1700s item in there. I'm pretty sure nothing in 1600s or earlier, however. (moments later) I checked a few name possibilities (e.g. Lagrange) and found this 1786 book by L'Huilier in the bibliography. – Dave L Renfro Apr 06 '19 at 10:26
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    This rule of thumb is over 10 years old, hence too old, hence doesn't apply. Problem solved! – einpoklum Apr 07 '19 at 08:28
  • I am in a very fast moving field, but still when I submitted last year one of my examiners complained that i cited very little from pre2006, in particular commenting that i didn't reference any of the works from a particular conference in 1990. I think the oldest paper i cited was from 1906, and a cited a few from the 60s, but indeed those were the exceptions. I think the examiner's complaint was fair. Even fast moving fields need background, and a thesis unlike a paper is a place you have space to give it. – Frames Catherine White Apr 07 '19 at 21:48
  • If this were a rule, would we be banned from decomposing matrices (first described in the 1870s), or using the Fourier transform (1820s)? And even if these examples are "trivial" enough to not warrant citations, many modern fast-developing fields in computer science started in the 1950-1960s, so the papers which started the whole discipline are worthy of mention for a few short sentences in the introduction, in many cases. In many cases you are solving a general problem, for which there are already special cases solved several decades ago. Why not mention them? – vsz Apr 08 '19 at 06:11

8 Answers8

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References can be as old as they need to be to cover the material. I had some that were more than 30 years old. But if all of your references are "old," people are going to want to know why.

You must also be sure you cover the most current research in your field. A few in my own dissertation were for material published in the same year as my own work.

The link given in the comments and the revised question seems to be directed toward undergraduate research assignments, and the "ten years" reference is a part of an example assignment, not a requirement given by the Shapiro Library. The key idea in the link is that references must be "somewhat current."

For a thesis or dissertation, one must cover the field, including both early and very new research.

Bob Brown
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    Indeed, I suspect that when flipping through a typical issue of a typical journal in most any field, one will find several papers whose references include items listed as "to appear", or "forthcoming", or "under review", or "submitted", etc. – Dave L Renfro Apr 05 '19 at 13:24
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    "References can be as old as they need to be" -- while I agree, the link the OP posted suggests that there are assignments saying "Sources must be published in the last 10 years". – Ingo Apr 05 '19 at 13:27
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    @Ingo Well, yes, but that link seems directed at undergraduate research assignments, and in in fact, that "last ten years" bit is prefaced with, "If it’s a requirement for your assignment..." For a doctoral dissertation, one is expected to cover the field. – Bob Brown Apr 05 '19 at 13:31
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    Something worth mentioning might be the difference between referencing research results, where you want to try and have relevant recent material, and referencing ideas, which might predate their use in actual research. For example, In my Master's thesis I referenced a pre-1900 paper by Karl Pearson for an idea he discussed that was important for my research, but then referenced modern research papers for my actual implementation. Another example might be natural selection; depending on the context, Darwin is an obvious reference. – anjama Apr 05 '19 at 15:05
  • In physics it is not uncommon to cite a 60-100year old papers. – Sascha Apr 06 '19 at 10:13
  • You need to have read that paper because some examiner WILL ask you about it. – D Duck Apr 06 '19 at 11:17
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    When I was an undergraduate in the late 70's we were told about the Science Citation Index, and it was pointed out that "Newton, I" was still being cited. – Martin Bonner supports Monica Apr 07 '19 at 07:19
  • A simple example: One sentence in a letter from 1961 said something I was trying to do couldn't be done. That was the last published word on the topic (polishing calcite normal to the optic axis). Of course I'd spent several weeks trying it before managing to find a source. – Chris H Apr 08 '19 at 12:40
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There is no rule about the age of citations. For example in my PhD-thesis I quoted some math-papers from 1600s that were originally written in latin (but those were exceptions).

Much more relavant than the year is the content of a citation and that you cover the relevant literature.

Also, you might want to include a few (relevant!) citations from recent years in order to show that you did your reading not just at the beginning of your thesis and then ignored everything afterwards.

lordy
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    In math it is common to cite old papers. 1600s is indeed exceptionally old but it is not uncommon to cite 10-100 years old papers. – Yanko Apr 05 '19 at 19:22
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    I would say that it would be a bit unusual for a math paper to have most of its references under ten years old (unless the authors give only a very brief account of the context and there is only a handful of references in all). – tomasz Apr 05 '19 at 20:37
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    @Yanko Ten years is old? Jeez, kids today. I doubt I've ever written a paper (including the ones I wrote more than ten years ago) that didn't cite something at least ten years old. – David Richerby Apr 06 '19 at 17:58
  • But did you really read those papers written in Latin? – Dubu Apr 08 '19 at 12:33
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I have cited a book on farming by Columella from the 1st century CE.

It provided crucial evidence for the use of a word at that time. But I did not take the evidence as the final say on the matter. I also cited 15th century academic analysis of the evidence as well as 21st century work. There is a fundamental difference between saying

It is true because X says so

and

X says so, so let us analyse it and cite more recent opinions on whether it is true.

In any discipline it may be necessary to contrast older and younger opinions on the same subject, and you will have to do some work yourself to argue that any given source, whatever its age, is - or is not - reliable.

As it happens, I rejected all the academic analysis and accepted my own interpretation of the original evidence. You as a researcher are expected to determine on a case-by-case basis what evidence needs to be cited, and what can be accepted.

Of course, at some stage, you have to accept that a certain claim is true because X says so. To do this you have to cite something that is fairly recent (which will depend on the discipline) and, if it not the most recent, argue why you are accepting it in preference to the most recent.

David Robinson
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Your rule has a large fraction of exception that you should always consider. Make sure you cite the relevant papers for your claims and that you cite the papers which were the first introducing the idea. Don't cite a textbook for ideas just because they are recent. Instead, try to find and cite the original works.

If you cite an idea originating back to Aristoteles it does not make sense to use a recent source. The idea is that old! Also, if you want to prove your claim, that some method was used in the 70s, it's useful to cite papers written in the 70s.

Dimitri Graf
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usr1234567
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    This hits what I consider the key point. Each citation should be appropriate for its purpose. Documenting the origins of a question is different from documenting the state of the art in a rapidly changing research area. – Patricia Shanahan Apr 05 '19 at 22:54
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The rule you quote is total nonsense for the sciences, and I have a hard time taking it seriously for the humanities.

You cite whatever you need to cite, regardless of its age. Typically, if you're referring to something that is decades old, it's now either common knowledge (e.g., Newton's laws) so probably doesn't need citation at all, or it's in textbooks (which are probably more appropriate to cite than the original source). Both of those things are a consequence of age but age per se is a completely spurious reason to not cite something.

David Richerby
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    In the humanities it's outright laughable. Besides the fact that often our sources are necessarily quite a bit older (classicists will quote stuff from antiquity, medievalists from the medieval, etc, historians from their period of history), many things we study may only be taken up by someone every few years or decades even, so to even do a cursory review of prior work you're going to be citing old stuff unless you're on a very popular topic. – user0721090601 Apr 07 '19 at 14:03
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    @guifa That's what I figured, but I was waiting for somebody else to say it, since "Scientist guesses what the humanities are like" is probably pretty laughable, too! – David Richerby Apr 07 '19 at 15:16
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A group of researchers published this very interesting paper:

The nearly universal link between the age of past knowledge and tomorrow’s breakthroughs in science and technology: The hotspot

From a pure data science perspective, they try to understand how the distribution of reference age affects the forward citations of an article. They analyze all publications (~ 28 million) in Web of Science published between 1945 - 2013.

Unfortunately, they do not show an aggregated histogram of age differences between a publication and its references. But in Fig. 1 we see the mean (0-50 years) and variance (0-4) for all published papers and it is all over the place. So the take away might be to cite what you want.

However, they echo in their paper the comments and answers that you got here. Impactful and hopefully good research seems to differ from the "cite what you want" approach. If you want to increase the likelihood of your work having an impact you should base your work on recent advances but also be aware of well-established theories or overlooked ideas from the past. They show this in the paper by finding a hotspot of highly cited papers that have a low mean age distance to their references but a high variance in age distance.

Here is a link to the paper (super interesting): http://advances.sciencemag.org/content/advances/3/4/e1601315.full.pdf

Dimitri Graf
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There's no limit on how old they can be. In biology people often cite Darwin (1859) and geneticists who work on pedigrees can cite government records from hundreds of years ago. Work involving theology may cite the Bible. Historians cite original documents from thousands of years ago. Sometimes a fun game is to see what the oldest citation you can get away with is. Plato or Aristotle is often a safe bet.

Generally, you are supposed to cite the oldest paper that made a discovery, as the credit belongs to them. When in doubt, you can cite one old and one new paper.

However, your work must be in the context of contemporary scientific literature. If you cite a 50 year old paper for a theory, you better make sure the theory has not been disproven in another paper published 30 years after. If you say the state of the art in a field is a paper published 10 years ago, it would look really bad if somebody brought up a 5 year old paper that advanced it further. This is why citing old material is risky: You can't easily tell that it's still current. If a paper came out last monday, chances are pretty low that somebody refuted it in that time.

Trusly
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  • I'm sorry but this is terrible. You seem to be advocating not citing older work that you use, purely to avoid the embarrasment of being out of date. That's what you literature search is supposed to avoid. If you're using the 50-year-old theory, you need to cite something for it. If that theory has been refuted, you're going to look like an idiot whether you cite the original paper or not. If you're out-of-date on the state of the art, you need to find out what it really is. And that paper that came out last Monday also hasn't had time for anyone to check that it seems to be true! – David Richerby Apr 06 '19 at 17:55
  • @DavidRicherby I'm sorry but your comment is terrible. You seem to have confused a number of points. Notable among them is your mistaking numbers given as examples for actual universal rules. I'd recommend re-reading the post carefully. If you still have questions, I'd be happy to respond to them if you phrase it in a more constructive manner. – Trusly Apr 08 '19 at 04:19
  • I've re-read your answer and I stand by what I wrote. I'm not criticizing the numbers at all. I'm criticizing what appears to be a recommendation to avoid citing old stuff because it might be out of date and your literature search might have failed to spot that. If that's not what you meant, what did you mean? – David Richerby Apr 08 '19 at 08:41
  • @DavidRicherby I didn't say to avoid citing old stuff because it might be out of date. I said that when citing old material, it is especially important to make sure it's not obsolete. – Trusly Apr 09 '19 at 19:47
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To be honest, just like you’ve said, all of this is quite subjective... Personally, I believe that if a paper is relevant to the point you are trying to make and hasn’t been categorically disproven then it’s fair game. However, what I think is irrelevant; it depends on the person marking your dissertation and how they feel about it. Some academics I know don’t care while others do. I was once marked down for using a 7 year old paper as a reference even though it was very relevant to my work, simply because the lecturer marking my work didn’t want to see anything older than 5 years.

For the most part, it should be fine. Academics who insist on only recent papers are few, in my experience.

Sule
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