University of California, San Diego: Edward Bender and S. Williamson's "Arithmetic, Logic and Numbers, Unit SF: Sets and Functions"

Read pages SF-1 through SF-8 for an introduction to sets, set notation, set properties and proofs, and ordering sets.

Click https://s3.amazonaws.com/saylordotorg-resources/wwwresources/site/wp-content/uploads/2011/09/CS202-Sets-and-Functions-Edward-Benderand-S.-Gill-Williamson.pdf link to open resource.