ElementaryMathExamples-mstack11

test for : mstack charalign="center"

W3C sample	WIRIS
	$\text{a}\text{abc}\text{d}\text{a}\text{b}\text{c}$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mstack charalign="center">
    <msrow>
      <mtext>a</mtext>
      <mtext>abc</mtext>
      <mtext>d</mtext>
    </msrow>
    <msrow>
      <mtext>a</mtext>
      <mtext>b</mtext>
      <mtext>c</mtext>
    </msrow>
  </mstack>
</math>

Author: Yecheng Gu