The XML Bible
Elliotte Rusty Harold
IDG Books, 1999
ISBN: 0-7645-3236-7
This presentation: http://metalab.unc.edu/xml/slides/jaoo99/xsl/
Chapter 14 of the XML Bible: http://metalab.unc.edu/xml/books/bible/updates/14.html
XSL Transformations Specification: http://www.w3.org/TR/xslt
XPath Specification: http://www.w3.org/TR/xpath