The Extensible HyperText Markup Language (XHTML) Tutorial
http://www.juicystudio.com/tutorial/xhtml/index.asp
  peer-reviewed

Lemon, Gez
Juicy Studio
2009

Abstract:

The Extensible HyperText Markup Language (XHTML) is intended to be a replacement for HTML. XHTML has a stricter syntax than HTML and is the official recommendation. of the W3C. XHTML was required due to the poor standard of some HTML documents due to the forgiving nature of browsers. This tutorial discusses the issues in making your documents XHTML compliant.