XPath, XML Namespaces in PHP, Xpath Checker Firefox addon, XPath pattern matching tutorial

XML Namespaces
http://www.jclark.com/xml/xmlns.htm

13 XPath axes
http://www.xmlplease.com/axis#s2.6

addon: good: Xpath checker for firefox
https://addons.mozilla.org/en-US/firefox/addon/1095

Pattern Matching in XML
http://www.oreillynet.com/xml/blog/2007/03/pattern_matching_with_xml_1.html

bbn: registering namespace: Namespaces in PHP
http://people.ischool.berkeley.edu/~felix/xml/php-and-xmlns.html

xpath tutorial examples
http://www.zvon.org/xxl/XPathTutorial/Output/examples.html

XmlDataSource: XPath Workaround For Default Namespaces
http://jasonf-blog.blogspot.com/2006/08/xmldatasource-xpath-workaround-for.html

How XPath Works
http://java.sun.com/j2ee/1.4/docs/tutorial/doc/JAXPXSLT3.html

XML (Programming PHP)
http://hell.org.ua/Docs/oreilly/webprog/php/ch11_01.htm

Parsing RDDL documents with PHP
http://www.ibm.com/developerworks/library/x-tiprddlphp/index.html

OOMPH - A Microformats Toolkit
http://www.codeplex.com/Oomph/Release/ProjectReleases.aspx?ReleaseId=18505

XML Namespace and How They Affect XPath and XSLT
http://developers.slashdot.org/developers/02/05/30/002252.shtml?tid=156
http://msdn.microsoft.com/en-us/library/ms950779.aspx

Fashion your firefox
https://addons.mozilla.org/en-US/firefox/fashionyourfirefox

SketchPath 2.0 - The XPath Tool
http://pgfearo.googlepages.com/