Display:

$\int_0^a f(x)\,d x$

Source:

<apply>
     <int/>
     <bvar>
          <ci> x </ci>
     </bvar>
     <lowlimit>
          <cn> 0 </cn>
     </lowlimit>
     <uplimit>
          <ci> a </ci>
     </uplimit>
     <apply>
          <ci> f </ci>
          <ci> x </ci>
     </apply>
</apply>