What books deal with gith (any variety) and the astral plane?


I am looking for inspiration for a gith based campaign in 5e and hoping that people can point me to whatever official books contain gith (of either persuasion) or the astral plane in which they live as focal points.

I am only interested in narrative so the edition doesn’t matter much, although I do appreciate that some things have changed through the editions.

While this might be seen as a ‘do the work for me’ question I think it is my only choice because buying every book from earlier editions will get expensive fast. The books can be any type (including novels) as long as they contain official lore about the gith.

The only book I am aware of containing much is Mordenkainens from 5e, which is what inspired the campaign. I am also aware of this question regarding the astral plane.