mi3

W3C sample	WIRIS
	$x \overset{maps to}{\to} y$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mi>x</mi>
    <mover>
      <mo> &#x2192;</mo>
      <mtext>maps to</mtext>
    </mover>
    <mi>y</mi>
  </mrow>
</math>

Author: Wolfram Research