<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE math PUBLIC "-//W3C//DTD XHTML 1.1 plus MathML 2.0//EN" "http://www.w3.org/Math/DTD/mathml2/xhtml-math11-f.dtd">

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mn>&foo;</mn> 
</math>