ElementaryMathExamples-msline10

test for : msline mslinethickness="thick" (with mathsize="18pt")

W3C sample	WIRIS
	$424+33$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mstyle mathsize="18pt">
    <mstack>
      <mn>424</mn>
      <msrow>
        <mo>+</mo>
        <none/>
        <mn>33</mn>
      </msrow>
      <msline mslinethickness="thick"/>
    </mstack>
  </mstyle>
</math>

Author: Yecheng Gu