ProofWiki is an amazing resource for someone studying CS and math like myself. Definitions and lemmas are hyperlinked and the proof style is very clear. They ev

ProofWiki is an amazing resource for someone studying CS and math like myself. Definitions and lemmas are hyperlinked and the proof style is very clear. They even have multiple proofs for the same theorem. For instance[0], and they have a wide range of deeper topics such as measure theory[1]. Good proof style is like good program style, if you use a big hammer of a theorem (cf. library function), you risk making the result more opaque to the reader than necessary. Proof 1 of [0] can be understood by essentially following the definitions whereas proof 2 uses Orbit-Stabilizer, but the argument is still quite slick. [0] https://proofwiki.org/wiki/Number_of_Distinct_Conjugate_Subsets_is_Index_of_Normalizer https://proofwiki.org/wiki/Number_of_Distinct_Conjugate_Subs... [1] https://proofwiki.org/wiki/Pointwise_Convergence_Implies_Convergence_in_Measure_on_Finite_Measure_Space https://proofwiki.org/wiki/Pointwise_Convergence_Implies_Con...