In case anyone is interested, these are the sources from which I drew my information for my Intro to XPath presentation.
http://www.w3.org/TR/xpath
http://www.zvon.org/xxl/XPathTutorial/Output/
http://www.w3.org/1999/11/xslt-xpath-pr
http://hotwired.lycos.com/webmonkey/98/43/index2a_page3.html
XML for the World Wide Web - required book
XSLT Quickly - optional book