Display:

$\sum_{x=a}^b f(x)\sum_{x\in B} f(x)$

Source:

<apply>
     <sum/>
     <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>
<apply>
     <sum/>
     <bvar>
          <ci> x </ci>
     </bvar>
     <condition>
          <apply>
               <in/>
               <ci> x </ci>
               <ci type="set"> B </ci>
          </apply>
     </condition>
     <apply>
          <ci type="fn"> f </ci>
          <ci> x </ci>
     </apply>
</apply>