Every "proof" of Godel's incompleteness theorem I've found online seems to stop after what I would consider to be the introduction. I find myself saying "yes, good, you've shown that it suffices to prove this fixed point theorem... now where's the proof of the fixed point theorem, surely that's the actual meat of the proof?" Anyone have a good source that shows the full proof, including why for a particular encoding of sentences as numbers the function "P -> P is not provable" must have a fixed point?