Formatting of right hand side of equation should be identical to formatting of left hand side
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <msub>
    <mi>A</mi>
    <mi>B</mi>
  </msub>
  <mo>=</mo>
  <msub>
    <mrow>
      <mi>A</mi>
    </mrow>
    <mrow>
      <mi>B</mi>
    </mrow>
  </msub>
</math>
Author: George Chavchanidze, Opera Software ASA