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I suppose most of you are familiar with the Mathematics Subject Classification (MSC). Particularly, when submitting an article for publication one has to choose appropriate classification codes.

But I am wondering if it does play a significant role in searching for literature on a specific subject, e.g. through MathSciNet or ZBMATH. Or do you prefer searching by subject terms?

Thank you very much!

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I think this is a very important and interesting question (as I suspect the answer is overwhelmingly 'no'), but I also think it's very poorly suited to MO, which is not really designed for polling mathematicians' opinions. Voting to close. – HJRW May 7 '12 at 14:26
I would vote to reopen if this was made a community wiki. Similar questions like this one… were discussed (and kept open) on MO in the past. – Vitali Kapovitch May 7 '12 at 17:04
Please start a discussion on meta if you would like to reopen. – HJRW May 8 '12 at 5:43
Honestly, I only wanted to get an impression on the actual use of MSC. I am not in the mood to hold a meta discussion on whether or not to reopen my question. – kassandra May 8 '12 at 12:11
@kassandra, I think it is right place to ask since you want to see opinion of professional mathematicians, but you should make it "community wiki". – Anton Petrunin May 8 '12 at 18:44
up vote 18 down vote accepted

At first, I thought this was a silly question, and it seemed highly implausible that searching by MSC code could actually be good for anything. Certainly it's a terrible way to find specific information, but I just gave it a try and it's quite a bit more useful than I thought. I put 52C17 in MathSciNet and got a list of 731 papers, and I've just been browsing through them and learning about a number of interesting papers I was unaware of. I should do this more often.

So my answer is that it's a waste of time if you're looking for anything in particular, but it can actually be a good way to get an overview of what's been happening recently in an area.

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Henry, thank you very much for your response. I think the best that can happen to a question is that it sets off reflecting on something and gives way to a try. Obviously, there is a lot of agreement with your answer. – kassandra May 14 '12 at 8:09

No. It never occurs to me to use the MSC when searching, and I don't know why I'd want to use it rather than search for specific terms.

When I have to list MSC codes for my own publications, I often find that they don't seem to fit very well. I'm sure I couldn't design a better classification, but as a search tool it seems to me to have outlived its usefulness. Maybe there are other uses.

(For comparison, which is better: a system where you type "guacamole recipe" into a search engine, or a system where you first learn that 381798.45 is the Thing Subject Code for "Mexican food", then browse the list of all web pages with code 381798.45?)

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Perhaps it depends on whether you have come across guacamole before you decide to find out more about Mexican food... – Yemon Choi May 12 '12 at 17:45
Less facetiously: it was by browsing old Pitman notes in the functional analysis section of a library that I learned there was such a thing as Lidskii's theorem for II_1 Von Neumann algebras; I would never have thought to type those terms into a search engine, before I learned there was something there to be searched for – Yemon Choi May 12 '12 at 17:49
Tom, this is indeed a comprehensible argument, which is convincingly illustrated by a "tasty" example, but Yemon's comment beautifully shows that there is some evidence of the MSC in the case that one cannot use a known term search. – kassandra May 14 '12 at 8:10
Fine, no problem. I'm not saying that no one else is allowed to find MSC codes useful, or that I couldn't make more use of them myself, just that (in answer to your original question) they're not something I do ever use. – Tom Leinster May 14 '12 at 14:57
I sometimes find MSC useful to narrow down a search involving terms that are used in multiple fields with different meanings. – Mark Meckes Jul 13 '12 at 18:42

I get emails from the AMS listing new publications in my area ( and that works by MSC code (I get everything under classification 55 = algebraic topology). This is still of some use, but less so than the equivalent arxiv emails (I get everything under This is the only use that I make of MSC codes.

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Neil, you wrote "This is the only use ..." but keeping up-to-date in a somewhat broader sense and not restricted to one's own specific research field seems to be more than most of us do today. – kassandra May 14 '12 at 8:11

MSC codes are a nice way to keep an eye on what's appearing in your area. Back in the "bad old day" before online MathSciNet and the ArXiv, I used to go to the library every month or two and skim all of the Math Reviews in 11D and 11G, and I reasonably frequently found articles of interest that I would then go read. Now I'm a bit lazy, but at least a few times a year I'll bring up all the 11G and 37P reviews and skim the titles, then look at the reviews of the ones that seem interesting. (Of course, these days often I already know about them from the ArXiv.) So I guess I'm echoing some of the other responses in saying that if you're researching a particular topic, searching on key words is much better, but if you want a general overview of what sorts of things people in your area are working on, it can be quite instructive to look at titles (and reviews) in an MSC category. BTW, there's a feature on MathSciNet that lets you bring up articles whose reviews have appeared in the past month(s). This is useful, since otherwise there will be a lot of articles that appear in the list that are waiting to be reviewed.

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Joe, your answer confirms my impression that the idea of keeping up-to-date in a field that is outlined by a classification code is definitely worthwhile. – kassandra May 14 '12 at 8:12

In the UK we have a group called MAGIC ( which runs graduate level courses in mathematics shared by video across 19 universities. In the early planning stages for that project (about 2005) I downloaded from MathSciNet lists of BiBTeX entries for all papers published by the participating universities in the previous decade, and sorted them by MSC code to get a systematic overview of the research activity across the network. That was quite a useful exercise.

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Tom wrote "Maybe there are other uses." Neil, here you brought a completely new aspect to the discussion: a use of the MSC in a certain project context. Does somebody know further projects involving the MSC or making use of it? – kassandra May 14 '12 at 8:13

If I were starting research into a field, or had to write a survey paper as a project, or recommend a breadth-oriented course of study to a student, I might do a search based on MSC codes. Usually my research interests are more focussed. Also, there are other ways of searching that would help the projects listed above.

One place where the codes might be useful is in generating glossaries by subject area. One could use a text processing system to form data points by code, number of occurrences, and so on, and use other means of preprocessing to come up with a reviewable list which could be hand annotated. I think a thesaurus for each major subject area would be quite useful, especially if it indicated historical usage.

Gerhard "Ask Me About System Design" Paseman, 2012.05.11

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Oh, Gerhard, you interestingly mentioned the term "thesaurus". Many subjects do come up with sophisticated thesauri, but due to my knowledge there is no community established thesaurus (in its proper meaning) in mathematics. – kassandra May 14 '12 at 8:14

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