rguments except base, but leaves both
   attributes unchanged within base.
   -->
    <math>
      <mstyle displaystyle="true">
        <msub>
          <munder><mo>O</mo><mo>O</mo></munder>
          <msub><mo>O</mo><mo>O</mo></msub>
        </msub>
        <msup>
          <munder><mo>O</mo><mo>O</mo></munder>
          <msub><mo>O</mo><mo>O</mo></msub>
        </msup>
        <msubsup>
          <munder><mo>O</mo><mo>O</mo></munder>
          <msub><mo>O</mo><mo>O</mo></msub>
          <msub><mo>O</mo><m