The original website is
http://www.quantitativefinanceservices.com/OpenDir/WINGslib/WINGToc.html
and it had the following notice at the bottom:
Copyright (c) 2010 Permission is granted to copy, distribute and/or modify
this document under the terms of the GNU Free Documentation License, Version
1.1 or any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A
copy of the license is included in the section entitled "GNU Free
Documentation License".
So we are fine.
Svetlana Tkachenko