Book of Proof, by Richard Hammack. This is one of the textbooks currently being used in MHF3202 Sets and Logic.
Taking and Using Notes in a College Math Class
Sets and Functions
Difference Between Inverse Functions and Inverse Images
What is a proof?
Mathematical grammar and correct use of terminology Inductive proofs: some common mistakes and misconceptions Peano Axioms for the Natural Numbers . In this handout, the symbol "\(\subset\)" means "subset" (as was completely standard until the late 20th century), not "proper subset".