msqrt6

nested simple sqrt

W3C sample	WIRIS
	$\sqrt{-1}$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <msqrt>
    <mrow>
      <mo>-</mo>
      <mn>1</mn>
    </mrow>
  </msqrt>
</math>

Author: Wolfram Research