Section 12.3 Reference Topics

A review of counting principles including the fundamental counting principole, permutations, combinations, and distinguishible permutations.
This is the elementary version:
http://www.mathagonyaunt.co.uk/STATISTICS/ESP/Perms_combs.html
This is the slightly more advanced version:
http://www.richland.cc.il.us/james/lecture/m116/sequences/counting.html

This site shows a table contrasting the basic counting types of problems.
http://www.math.hawaii.edu/~ramsey/Counting.html

This (somewhat advanced) site is very good if you take some time to understand how to use it. By selecting the second object icon (at the top of the page), you go to an index page. From this index you can find information on permutations, combinations, or distinguishible permutations.
http://www.theory.csc.uvic.ca/~cos/root.html

Links