
<!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>
  <eq/>
  <apply><laplacian/>
    <ci> f </ci>
  </apply>
  <apply>
    <divergence/>
    <apply><grad/>
      <ci> f </ci>
    </apply>
  </apply>
</apply>
</math>