Old Dominion University: Shunichi Toida's "Set Theory"

Introduction to Set Theory
Representation of Sets
Basics of Sets
Mathematical Reasoning

Read these pages, which discuss the basics of set theory. Note that there are three ways to define a set. The third method, recursion, will come up again later in the course, but this is a great time to learn it.

Click http://web.archive.org/web/20160417054637/http://www.cs.odu.edu/~toida/nerzic/content/set/intr_to_set.html link to open resource.