see this answer: http://mathoverflow.net/questions/102463/ideals-of-etale-structure-sheaves/103142#103142.

[Spe] David Speyer (mathoverflow.net/users/297), Rhombus tilings with more than three directions, MathOverflow, http://mathoverflow.net/questions/78302 (version: 2011-11-09).

http://mathoverflow.net/questions/27345/norms-of-commutators

is referenced in this paper by Ozawa, Schechtman and me on the arXiv.

I didn't ask him how long he had had the cards or how many he had given out.

Also, I think Anton and the MathOverflow founders have become ambassadors between academia and some new variety of social networking, except they are smart enough to focus on doing the narrow task (operating the forum) well, and putting the ambassadorial and other tasks on the back burner ( or at least making many of them much less visible to some of us ). I think they are becoming part of a culture that involves things much more alien to academics than business cards.

Gerhard "Prefers Handing Out Business Pens" Paseman, 2011.11.11

I don't think this is quite right; the culture of mathematics as I've experienced it has no place for business cards. I would seriously weirded out if a mathematician gave me their business card in almost any context (I don't get business cards from non-mathematicians much either). It's even weirder than wearing a suit (which of course a reasonable number of mathematicians do with some regularity; it's just that rest of us regard this eccentric behavior on their part).

If you are interested in how to handle similar issues, let me know; you can contact me via my more recent email address which Scott Morrison should still have.

Congratulations on your presentation.

Gerhard "Ask Me About System Design" Paseman, 2011.10.24

The summit was great fun. I talked a lot to Richard Price (who is behind academia.edu) and the folks behind ScienceExchange.

I didn't have business cards to hand out, but I couldn't give a good explanation of why not. For some reason, mathematicians don't exchange business cards as much as other people do.

http://mathoverflow.net/questions/60174/factorization-of-a-real-matrix-into-hermitian-x-hermitian-is-it-stable/60188#60188

and once for my question about norms of commutators

http://mathoverflow.net/questions/27345/norms-of-commutators

http://www.math.rutgers.edu/~zeilberg/mamarim/mamarimPDF/pmn.pdf

which mentions:

http://mathoverflow.net/questions/71092/how-many-integer-partitions-of-a-googol-10100-into-at-most-60-parts

(See also the accompanying meta thread for the long history of this post.)

Thanks joro for pointing this out.

Gerhard "Ask Me About System Design" Paseman, 2011.05.10

Anyway, I just wanted to mention that at Warwick on Monday after a lecture I gave to their undergrad Maths Society, I was told that they've started inviting UK MOers to give talks this year. I think of this a success story for MO!

1. San Jose Mercury News, Stanford and UC Berkeley create massively collaborative math
2. The Daily Californian, Student's Site Connects Mathematicians Worldwide

http://search.arxiv.org:8081/?query=%22math+overflow%22+OR+mathoverflow&in=grp_math

Let's agree on some citation guidelines, and I'll include them in the attribution page

I think it may be a good idea, but it should make clear the distinction between republishing (action possible under cc-wiki license; and I'm not aware of how we could change any of its requirements) and citing (something done voluntary by mathematicians on ethical basis; and the format of which this thread discusses).

The first concept is only applicable if you're copying the text; the copyright law (I'm not a lawyer, but this idea is quite clear and well-known) doesn't protect ideas, mechanisms or algorithms (note that patent law sometimes does).

For example, suppose nobody knew how to calculate some function f(x) at x = 137 and finally Smarty S. was able to provide a long calculation that established that f(137) = 12. It doesn't matter where s/he did it — in a journal, on the web, in a talk: both before and after, anyone is able to talk about the value of f(137) and speculate about it being equal 12, or claim it being 12 or 13. After the result is posted, nothing in the copyright law prohibits saying "f(137) is known to be 12 (see reference)".

I don't think therefore that there could be any legal requirement for citations that Math Overflow could impose, unless some part of the text is copied. However, ethically, it's well-established in mathematics that you should cite other people's ideas, for two reasons: (1) you shouldn't pretend you did something when it's actually another person and (2) if the statement is non-trivial, you need to give readers the ability to see its proof or the source.

Since we aren't sure about the sitewide policy, perhaps the best thing would be to ask the person who answered in each case, especially if a person is normally pseudonymous. I personally would go for something like

[10] Communicated by David Speyer on MathOverflow (/questions/11851).

http://mathoverflow.net/questions/11851

See this very similar discussion on meta.MO.
answered Jan 15 at 11:52, David Speyer (/users/297)

But I think it should be fine to just include the number of the post and the name of the user if it's a pain to include the user numbers, since that is enough information to track down the source. I'll look into the possibility of including the URLs of the posts and the user numbers automatically whenever you send an MO page to your printer (or print to a file). It's also worth noting:

• I'm not a lawyer, but I think including an answer in a hand out or lecture slides would count as fair use, so you're not legally required to clear all the hurdles the copyright holder sets up. Those requirements are there to keep people from blatantly taking MO content and selling it in some way. Citing MO precisely is primarily a courtesy to your audience (so they can track down the source) and to the author of the material.
• You can always skip the hurdles if you get permission from the copyright holder (the author of the post).

There is an attribution page (linked to from the bottom of each MO page) listing what you should do if you want to republish any content. If you're just citing or paraphrasing something that happened on MO, I'd include the following information:

• The name(s)/user number(s) of the person who posted the material you're using (e.g. "Greg Kuperberg (http://mathoverflow.net/users/1450)").
• A link to the question/answer, of the form http://mathoverflow.net/questions/12345, where 12345 is the number of the post. As Qiaochu points out, you don't have to include all the stuff after the number; that stuff is just there to make it easier for Google to understand what the page is about. Also note that if post number 12345 is an answer rather than a question, the above URL will redirect to the right place.

I don't see any downside to linking to the specific post or page that you're using, even if there's a chance it disappears. It doesn't stop people from citing impossible-to-find papers. Btw, does anybody have a copy of Artin's Algebraization of formal moduli I they could send me?

Let's agree on some citation guidelines, and I'll include them in the attribution page. Is there some way I should make the attribution page more prominent?

Personally I think that if MO helps you with your research, then acknowledging that in print

• is polite,
• is helpful to your readers (who can look it up),
• helps MO to carry on being funded,
• attracts new people to MO,
• costs nothing.

I probably agree with you that in the reference list, the citation should be for the person, not MO itself - but the source should be given as a particular MO page, e.g. in the way that Scott describes.

Personally, I wouldn't hesitate to cite a particular MO page, using the convention of adding "Accessed DDMMYYYY" when citing (potentially mutable) webpages. What objections do people have to doing this, and can we resolve these objections?

I'd like to see such references for two reasons. One, I think it's more useful to the reader. They can actually go read the discussion, instead of being potentially frustrated by an opaque reference to a private conversation.Two, it's great advertising for MO!

• David Brown did an interview with a Canadian journalism student.
• Tom Leinster over at the n-cat cafe, on a problem solved with some help from Mathoverflow.
• David Brown mentioned MO in the acknowledgments of a recent paper