<?xml version="1.0"?>
<!DOCTYPE mrow SYSTEM "mathml.dtd" [
   <!ENTITY alpha "alpha">
]>

<mrow>
<msup>
  <msub>
     <mi>x</mi>
     <mn>1</mn>
  </msub>
  <mi>&alpha;</mi>
</msup>
        <mo>+</mo>
        <msubsup>
          <mi>x</mi>
          <mn>1</mn>
          <mi>&alpha;</mi>
        </msubsup>
</mrow>
