<?xml version="1.0" encoding="UTF-8"?>

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">  <munder>    <mi mathvariant="normal">middle</mi>     <mi mathvariant="normal">bottom</mi>   </munder>   <mo>=</mo>   <munderover>    <mi mathvariant="normal">middle</mi>     <mi mathvariant="normal">bottom</mi>     <mphantom>      <mi mathvariant="normal">fail</mi>
    </mphantom>   </munderover> </math>