This presentation: http://www.cafeconleche.org/slides/sd2005west/xmlfundamentals
XML in a Nutshell, third edition
Elliotte Rusty Harold and W. Scott Means
O'Reilly & Associates, 2004
ISBN 0-596-00764-7
XML 1.1 Bible
Elliotte Rusty Harold
Wiley, 2004
ISBN 0-7645-4986-3