Copyright (c) 2002-2004, Stephen Ferg This work is licensed under the Creative Commons Attribution 2.0 License. You are free to copy, distribute, and display the work, and to make derivative works (including translations). If you do, you must give the original author credit. The author specifically permits (and encourages) teachers to post, reproduce, and distribute some or all of this material for use in their classes or by their students. http://creativecommons.org/licenses/by/2.0/