Copyright © 2004 - 2012 Richard Macwilliam all rights reserved. This work is licensed under a Creative Commons License. You may copy, distribute, display,and perform this work without contacting me provided you give me credit (include my name or a link to my site), do not use the work for commercial purposes and do not alter, transform or build upon the work. For more information go to: http://creativecommons.org/licenses/by-nd-nc/1.0/

Schools: you can also build upon the work and use the work commercially provided you contact me to get my approval (I always approve genuine requests).