<math xmlns="http://www.w3.org/1998/Math/MathML">
<apply>
<int/>
<bvar>
<ci>x</ci>
</bvar>
<lowlimit>
<ci>a</ci>
</lowlimit>
<uplimit>
<ci>b</ci>
</uplimit>
<apply>
<ci type="fn">f</ci>
<ci>x</ci>
</apply>
</apply>
</math>
Author: MathML 2 Recommendation