Sum as x goes from a to b of f(x)
<math xmlns="http://www.w3.org/1998/Math/MathML">
  <apply>
    <sum/>
    <bvar>
      <ci>x</ci>
    </bvar>
    <lowlimit>
      <ci>a</ci>
    </lowlimit>
    <uplimit>
      <ci>b</ci>
    </uplimit>
    <apply>
      <fn>
        <ci>f</ci>
      </fn>
      <ci>x</ci>
    </apply>
  </apply>
</math>
Author: Design Science, Inc. (E. Cannon, E. Tabacman, R.Miner)