I want to learn the background for the Gelfond Schneider Theorem:

https://en.wikipedia.org/wiki/Gelfond%E2%80%93Schneider_theorem

I want to learn the background needed for the proof of this theorem, as well as the proof itself. But I don't know what kind of textbook or class this would normally be covered in. Please recommend what I can study.

I want to be able to prove results on transcendence of specific numbers, which I know can be difficult in general. I also want to learn more about the subject in general, since my knowledge is very limited.

Thank you!!