Section 4.7 Reference Topics
This site gives a nice introduction to modular arithemtic and leads to the next
section on cryptography if you following the links on the site.
http://www.princeton.edu/~matalive/VirtualClassroom/v0.1/html/lab1/lab1_3.html
This site is a nice interactive site which deals with arithmetic (mod m).
Do not be frightened by the notation, the arithemtic table at the bottom is
interesting
http://www.cut-the-knot.com/blue/Modulo.shtml
Is there really such a thing as "infinity"?
http://www.math.toronto.edu/mathnet/plain/answers/infinity.html