Other sources of XML info:

• Understanding XML, from Sun's documentation
• The XML FAQ, from the University College Cork's site in Ireland on XML
• The W3's site on XML, containing the official specifications and some recommended reading
• xml.org, "The XML Industry Portal"

Links to groups with related information:

• Group 2, for information on SAX as well as DTDs
• Group 3, for information on DOM
• and, finally, the Informatics 344 course page.