XHTML Character Entity Reference
- A listing of many XHTML codes for non-standard ASCII characters.
- http://www.digitalmediaminute.com/reference/entity/index.php

HTML 4.01 / XHTML 1.0 Reference
- Element and attribute definitions and examples, with alphabetical index, and also sorting by function.
- http://www.w3schools.com/tags/

XHTML - Webopedia Definition and Links
- Describes and defines the term 'XHTML.'
- http://webopedia.com/TERM/X/XHTML.html

XHTML Basic Reference
- Complete reference with examples and relevant links to the W3C standard.
- http://zvon.org/xxl/xhtmlBasicReference/Output/index.html

XHTML 1.0 Reference
- Complete reference with examples and relevant links to the W3C standard.
- http://zvon.org/xxl/xhtmlReference/Output/index.html

HTML and XHTML Document Type Definitions
- This page lists and provides links to standard DTDs and SGML declarations for HTML and its successor language, XHTML.
- http://www.utoronto.ca/webdocs/HTMLdocs/HTML_Spec/html.html

Context Sensitive XHTML
- This paper tries to introduce some new elements into the HTML language. The purpose of these elements is to create documents that can contain different pieces of information at the same time. These various pieces of information can be presented to the use
- http://www.cg.tuwien.ac.at/~scheich/XHTMLPaper/overview.html

XHTML Modularization Overview
- An overview of the modularization of XHTML.
- http://www.w3.org/MarkUp/modularization