Pro Git: https://git-scm.com/book/en/v2
The Rust Programming Language: https://doc.rust-lang.org/book/ (the Rust standard library also has very comprehensive documentation)
Cocoa architecture: https://developer.apple.com/library/archive/documentation/Co...
Python: https://docs.python.org/3/tutorial/index.html (also pretty good standard library docs)
Scheme R5RS: https://standards.scheme.org/official/r5rs.pdf
Racket: https://docs.racket-lang.org/
SQLite: https://www.sqlite.org/docs.html