Is it possible to cite a page in n-Lab in a research paper? One of the concepts I need in my paper is best summarized on the n-Lab page. I tried my best to find a similar description of the same concept in a more "classical" reference, such as a paper or a book, but I can't. 
I have two questions:
(a) Is it "allowed" to cite n-Lab in a research paper? I mean, are people doing this? Would it make a referee frown?
(b) What is the format of citing a page from n-Lab?
 A: From https://ncatlab.org/nlab/show/FAQ#Citing:

How do I cite a page on the nLab?
You should, of course, include a link or URL to the page or pages that you wish to cite. You should also give the information about which version of the page you are citing, since pages change over time. The version number can be found as follows: look at the bottom of the page where it says “Back in time ($N$ revisions)”; the current version number is $N+1$.
You can link directly to the version you want to cite by using a url such as
http://ncatlab.org/nlab/revision/PageName/VERSIONNUMBER
We recommend that if you only include one URL, it be of the form show/PageName which will point to whatever version of the page is current when it is accessed. This is because pages generally improve over time, and whoever is following your reference ought to be taken to the best, up-to-date version of the page. Anyone who cares about finding the exact version of the page that you cited can figure out how to find it in the history.
On the other hand, if you can give two URLs (this would be cumbersome in a printed paper, but is possible with links on a web page), then it may be helpful to give the appropriate revision link as well as the show one.

Here's one possible BibTeX template, which is similar to what I've used in published papers:

@Misc{nlab:pagename,
  author =   {{nLab authors}},
  title =    {Page Name},
  howpublished = {\url{http://ncatlab.org/nlab/show/page+name}},
  note =     {\href{http://ncatlab.org/nlab/revision/page+name/N}{revision N}},
  month =    {Month},
  year =     XXXX}

The double-brackets around {{nLab authors}} cause the alpha citation style (which I prefer to the numbered one) to cite it as [nLaXX], which is not great but better than [autXX] if you put in only single brackets.  (Suggestions for improvements here are welcome.)  In some cases, if the page as it existed at the time of citation was largely the work of one person (perhaps with minor things like typo fixes from other contributors --- this requires looking through the page history version-by-version to find out), I have instead attributed it to that person "and others" in the BibTeX (producing "et. al." in the citation --- this is one situation in mathematics where I feel "et. al." is actually warranted).
Edit: All nLab pages now have a "Cite" link at the bottom that produces BibTeX according to my template!
A: You can cite an nLab entry much as many papers cite an online resource.  I recommend searching ArXiv and other published sources for examples of citation formats.
Since the Web is not static, I recommend not only that you specify a date retrieved, but that you make a personal copy of the (relevant portion of the) web page and include it in your archive of your paper. In particular, making a hard copy or a JPEG picture format might save you or some researcher in the future.
Gerhard "Preparing For The Future Onslaught" Paseman, 2018.04.20.
