Copyright ©2004 Chris Lale <feedback.chrislale@coolscience.co.uk>. Permission is granted to copy, distribute and/or modify this document with no Invariant Sections, with no Front-Cover texts and with no Back-Cover Texts under the terms of the GNU Free Documentation License, version 1.1 or any later version, published by the Free Software Foundation. A copy of the license can be found at http://www.fsf.org/copyleft/fdl.html.