<?xml version="1.0"?>
<!DOCTYPE html PUBLIC
  "-//W3C//DTD XHTML 1.1 plus MathML 2.0//EN"
  "http://www.w3.org/TR/MathML2/dtd/xhtml-math11-f.dtd"
[
  <!ENTITY mathml "http://www.w3.org/1998/Math/MathML">
]>
<math display="block" xmlns="&mathml;">
  <mi>f &#x0332;</mi>
  <mi>-</mi>
  <mo>+</mo>
  <mo> -</mo>
  <mo>&#x0332;</mo>
</math>
