## Reference Topics 2-4

*This site introduces the idea of infinite sets:*

http://mathforum.org/isaac/problems/cantor1.html

*This site introduces the idea that there are different sizes of infinity:*

http://www.math.grinnell.edu/~miletijo/museum/infinite.html

*A slightly more advanced discussion of sets can be found in the article, “A Crash course in the *… See the whole entry