
<!DOCTYPE math
  PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<math xmlns="http://www.w3.org/1998/Math/MathML">
<apply>
  <compose/>
  <fn><ci> f </ci></fn>
  <fn><ci> g </ci></fn>
</apply>
</math>