Citations in a math blog I am an incoming math PhD student in the US. I am thinking of starting a math blog. The intended audience is myself plus maybe other math graduate students.

I am a little concerned about citations to avoid plagiarism. Of course if a theorem or proof comes from a paper, I need to cite it. What about theorems and proofs coming from textbooks. For example, say I give a definition of a group, which appears in virtually all standard textbooks in introductory algebra.

I guess the latter case will happen more frequently since my blog is mostly entry level graduate material math that you can find in many textbooks.

Questions:


If a theorem or proof comes from a textbook, can I assume that it is considered common knowledge, with respect to the targeted audience, and just state and prove the theorem?
At what point does a theorem or proof stop becoming common knowledge, maybe it only appears in some very advanced textbooks?
Blog posts don't need to have a formal bibliography, but you should always provide attribution to others work, whether it is an original piece of research, or just a textbook whose presentation you are following. In a blog post, you can do this in a conversational style: point out results you enjoyed (with links!) and textbooks you find helpful. Not only will the folks you mention appreciate this, it will be helpful to your readers who want to follow up and learn more.