href3.test

<<< mml
<?xml version="1.0" encoding="UTF-8"?>

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>x</mi> 
    <mo>=</mo> 
    <mfrac href="http://mathworld.wolfram.com/QuadraticEquation.html">
      <mrow>
        <mo>&#x2212;</mo> 
        <mi>b</mi> 
        <mo>&#x00B1;</mo> 
        <msqrt>
          <mrow>
            <msup>
              <mi>b</mi> 
              <mn>2</mn> 
            </msup> 
            <mo>&#x2212;</mo> 
            <mn>4</mn> 
            <mi>a</mi> 
            <mi>c</mi> 
          </mrow> 
        </msqrt> 
      </mrow> 
      <mrow>
        <mn>2</mn> 
        <mi>a</mi> 
      </mrow> 
    </mfrac> 
  </mrow> </math>
>>> native
[ EIdentifier "x"
, ESymbol Rel "="
, EFraction
    NormalFrac
    (EGrouped
       [ ESymbol Bin "\8722"
       , EIdentifier "b"
       , ESymbol Bin "\177"
       , ESqrt
           (EGrouped
              [ ESuper (EIdentifier "b") (ENumber "2")
              , ESymbol Bin "\8722"
              , ENumber "4"
              , EIdentifier "a"
              , EIdentifier "c"
              ])
       ])
    (EGrouped [ ENumber "2" , EIdentifier "a" ])
]