My advise: cite everything which you do not prove in your paper, and which is not included in the standard undergraduate and graduate textbooks in the subject.

It absolutely does not matter whether the source passed a peer review or not. The crucial criterion for a citable source is that it must be AVAILABLE. (Published, posted in the internet). If you suspect that the thing is in EGA, search in EGA.

What is "common knowledge" and what is not strongly depends on the set of people that you consider. If you want your paper to be read by people, try to make it accessible to maximally broad set. O my opinion, a typical reader of a research paper is a graduate student in the same broad area.

My advise: cite everything which you do not prove in your paper, and which is not included in the standard undergraduate and graduate textbooks in the subject.

It absolutely does not matter whether the source passed a peer review or not. The crucial criterion for a citable source is that it must be AVAILABLE. (Published, posted in the internet). If you suspect that the thing is in EGA, search in EGA. (I suppose that EGA is not a standard graduate text book, otherwise you would have no difficulty searching:-)

What is "common knowledge" and what is not strongly depends on the set of people that you consider. If you want your paper to be read by people, try to make it accessible to maximally broad set. On my opinion, a typical reader of a research paper is a graduate student in the same broad area.

My advise: cite everything which you do not prove in your paper. It absolutely does not matter whether the source passed a peer review or not. The crucial criterion for a citable source is that it must be AVAILABLE. (Published, posted in the internet). If you suspect that the thing is in EGA, search in EGA.

What is "common knowledge" and what is not strongly depends on the set of people that you consider. If you want your paper to be read by people, try to make it accessible to maximally broad set.

My advise: cite everything which you do not prove in your paper, and which is not included in the standard undergraduate and graduate textbooks in the subject. 

It absolutely does not matter whether the source passed a peer review or not. The crucial criterion for a citable source is that it must be AVAILABLE. (Published, posted in the internet). If you suspect that the thing is in EGA, search in EGA.

What is "common knowledge" and what is not strongly depends on the set of people that you consider. If you want your paper to be read by people, try to make it accessible to maximally broad set. O my opinion, a typical reader of a research paper is a graduate student in the same broad area.