Thanks to my friends Colby Lemon and John Chodera, and my sister Annette Maxwell, for encouragement and feedback. Thanks to my longtime friend, Scott Tabbert, for his enthusiastic support, despite him not being a math person at all. And thanks to my housemate Kate McLaughlin-Williamson for valuable suggestions on the cover design. (Be glad I asked her for feedback. If you can stand to look at it for very long, you have her to thank.) These people only helped improve it, of course - if anything is less than ideal, that is my doing.
This book has been written entirely using open source software. The platform was a Debian GNU/Linux system, using either the icewm or the KDE window manager environments. Some other software used includes LYX and the LATEX typesetting system, The Gimp (for image creation and editing), the ImageMagick image processing tools, Perl (for making various support software), Subversion for document version control, the use-for-all-sorts-of-things tools such as emacs, vi, konsole, konqueror... and many others.
All of this software exists because, worldwide, developers I never met invested their time and energy to write software, with the purpose of freely giving it to anyone who wants to use it. This book simply would not exist in this form were it not for those developers' generosity. My tremendous thanks and appreciation to all of you.