Some guides say to limit the references to up to 5-6 years old.

But I've speculated as to, whether it's possible that research would become "deviated to pursuits for which in the history there existed multiple paths". I.e. since old research may suggest new research, but not all new research is necessarily "all research", then wouldn't it be possible to grasp an old article and then do new work on that?

I'd assume that this could be very feasible in mathematical papers for example. What about computer science papers? Something else?

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    Please indicate the field you are working in. As a mathematician, to me such a rule seems to be completely ridiculous.
    – Christian
    Commented Jul 8, 2020 at 9:18
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    Throw away those guides ;-) Commented Jul 8, 2020 at 9:19
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    Can you link to such guides? This sounds preposterous. Commented Jul 8, 2020 at 12:07
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    @user2705196 Out of curiosity, I found one such guide: "Be careful about citing old references. The rule of thumb is to go back at most five to six years" the 3rd line of the section "Some dos and don’ts of using references"
    – Nobody
    Commented Jul 8, 2020 at 12:53
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    There's some published research on citation age - here's a recent paper for the subfield of computational linguistics (aclweb.org/anthology/2020.acl-main.699.pdf); in the top venues of the field the mean age of citations is 5-7 years, with a significant number of citations being to 10+ year old; and the recent decrease of the mean from 7 to 5 years is considered troubling - so you definitely should not limit yourself to at most five to six years. On the other hand it would be very troubling if you have only old references.
    – Peteris
    Commented Jul 8, 2020 at 17:50

5 Answers 5


Taken at face-value, these guides are useless or even harmful, as they would promote an organized loss of memory and lead to multiple reinventions of the wheel.

It is also important, however, to show that your research is moving at the cutting edge of the field. This is probably where the advice you mention is coming from. You should demonstrate the topicality of your project by discussing the most recent literature to the extent that it is adequate for your research problem. Strategically, it may be useful to highlight your project's contribution to the latest research, including new trends, especially in the introductory section. But take care not to exaggerate this tactic, as it cannot compensate for substantive shortcomings and might even come across as superficial.

To explicitly answer the question in your title: References remain valid until superseded by later research with respect to the aspect they are cited for. To make that judgement, you have to know the field; to know the field, you have to read. Looking at the age of the reference cannot replace making that judgement, it can only give you a rough indication as to whether the reference is likely to have been superseded. The fact that different (sub-)fields move at different speeds makes it even less reasonable to put a number on a reference's shelf-life.

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    "References remain valid until superseded by later research." - I would add "with respect to the aspect they are cited for" to that sentence. With that addition, the statement is beautifully accurate for all cases, including the one where the reference is specifically cited for being old (think "The problem of thingsadoodling was of interest as early as in the 1870s (Mugglevich et al.)." With respect to its age, this reference never gets superseded by later research and thus always remains valid. Commented Jul 9, 2020 at 19:14
  • @O. R. Mapper Thanks, that's a welcome addition Commented Jul 10, 2020 at 6:08

As a mathematician, this sounds like terrible advice to me.

I would be slightly wary of a paper where every citation is 10 or more years old; but even then, I have seen cases where such a situation makes perfect sense, because someone found a way to pick up the slack on a research avenue that had stopped 10 or 20 or more years prior.

In a good research paper the results should build upon previous work, so some recent citations are expected. But I would also expect a decent review of previous work. If all citations are less than six years old, then the paper is likely either too technical or too shallow.

  • Thanks for the edits, guys. The first I thought I had corrected it myself, but I guess I didn't. Commented Jul 8, 2020 at 18:42
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    As another mathematician, I have cited papers from the 1800s. If a paper is correct, then it is correct. If it's relevant for your research, cite it. Commented Jul 9, 2020 at 7:32
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    "because someone found a way to pick up the slack on a research avenue that had stopped 10 or 20 years prior" - very true. It's not the authors' fault no-one has looked into a particular question in the meantime and they should not be punished for it. Commented Jul 9, 2020 at 19:17

It depends on the purpose of your reference. If you cite a paper to show the state-of-the-art, then older papers might be only acceptable for very niche fields, without too many publications. If you compare your results with an older paper, than you have to have a good explanation why such comparison is insightful.

If you refer to some general theory or idea, than older papers are still acceptable. I personally like to include the original paper for a given idea if the page limit allows it.

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    I strongly disagree that "older papers might only be acceptable for very niche fields, without too many publications". Hard open problems can stand for decades or centuries, even in fields with active research.
    – Nathan S.
    Commented Jul 9, 2020 at 5:08
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    @NathanS. Sure, if you remove the first conditional part of the sentence than I would disagree with it as well. In any practical discipline where something is realized, comparison should be made with the best results published so far. Comparing a the computational performance of the newest processors with one from the 80s have hardly any value of information. Similarly in medicine and psychology it would be strange as well to compare a result with one from the 70s. In very theoretical or descriptive fields that is not the case, but in such fields nobody would tell OP to forget any old article. Commented Jul 9, 2020 at 13:45
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    "comparison should be made with the best results published so far" - and sometimes, those best results are one or two decades old, even in practical disciplines. What do you want the authors to do in such a case? Compare with something else that is more recent, even if it is beside the point? Indeed, the computational performance of the newest processors is quite likely not an example of such a situation. Commented Jul 9, 2020 at 19:18

If you read it, and you relied on it for your research, then you have to cite it. To not cite it would be plagiarism.

Can you do good research without looking at anyone else's research that was published more than six years ago? Almost certainly not. Even if you were doing a review article on research from the last five years, you would want to contextualise that five years' research with the five/ten/fifty years before it.


As others have mentioned, this broad-stroke advice is sufficiently wrong in many disciplines to be useless as general guidance. Yes, of course you need to ensure you're up to date in your subfield, but above all you need to cite whatever is needed to ground your research conceptually and empirically, whatever its datestamp might be.

With that in mind, it's worth asking: when is such guidance valid in a nontrivial way? I have encountered it most often in the humanities or in interdisciplinary work with a humanities or social sciences element. A strong caution about old references is actually warranted in fields which have undergone major paradigmatic shift, especially where the old paradigms have been criticized for being biased or rooted in privilege.

If you run around quoting "old-school", Euro-centric papers on "Primitive Art" or South Asian civilizations, especially without engaging with the paradigmatic shift in (e.g.) postcolonial theory since then, you will (rightly) get skewered. Similarly, I have read then-respected scholarship in linguistics and psychology from a few decades ago that now makes us cringe. And woe betide you if you rely blindly on psychiatric research implicitly grounded in DSM versions <=4 (6 being most recent, I believe).

That doesn't mean you can't dig up something meaningful from the historical vaults even in such fields; just that you better know what you're doing and engage deliberately with material shifts since then. Therefore a simple heuristic of "don't do it" is, in those instances, helpful.

With that in mind (and in agreement with others answering), I'd actually turn your last paragraph around. Math is pretty simple in this regard; the only issue in quoting an old paper will be the obvious one: have you failed to note a more recent substantive advance; otherwise it's fine. It's not my field, but I would expect the shifts in computer science to be more significant. While not as big a deal as in many fields in the humanities, I think your risk of coming across as anachronistically irrelevant if you're relying significantly on old references are higher in C.S. than in math.

  • Speaking about computer science: it always amazed me, how certain books there do not age gracefully. As for the papers, they seem Ok. Either it's completely outdated (and then you would not read or cite it) or the idea is well and living (in which case it makes sense to stumble through ancient notation and such). Of course, mathematics is more for eternity, but many parts of CS age well. Commented Jul 11, 2020 at 16:12

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