rec-bvar1

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <apply>
    <apply>
      <csymbol cd="calculus1">nthdiff</csymbol>
      <cn>2</cn>
      <bind>
        <csymbol cd="fns1">lambda</csymbol>
        <bvar>
          <ci>x</ci>
        </bvar>
        <apply>
          <csymbol cd="arith1">power</csymbol>
          <ci>x</ci>
          <cn>4</cn>
        </apply>
      </bind>
    </apply>
    <ci>x</ci>
  </apply>
</math>

Author: MathML 2 Recommendation