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<html>
 <head>
   <title>invisible operators</title>
   <meta charset="utf-8"/>
 </head>
 <body>

   <!-- These examples are taken from http://www.w3.org/TR/MathML/chapter3.html#presm.invisibleops.
        The invisible operator glyphs should render as empty box and, per the operator dictionary, should not have space around them. -->
   <math>
     <mrow>
       <mi>f</mi>
       <mo>&#x2061;<!--FUNCTION APPLICATION--></mo>
       <mrow>
         <mo>(</mo>
         <mi>x</mi>
         <mo>)</mo>
       </mrow>
     </mrow>
   </math>
   <math>
     <mrow>
       <mi>sin</mi>
       <mo>&#x2061;<!--FUNCTION APPLICATION--></mo>
       <mi>x</mi>
     </mrow>
   </math>
   <math>
     <mrow>
       <mi>x</mi>
       <mo>&#x2062;<!--INVISIBLE TIMES--></mo>
       <mi>y</mi>
     </mrow>
   </math>
   <math>
     <msub>
       <mi>m</mi>
       <mrow>
         <mn>1</mn>
         <mo>&#x2063;<!--INVISIBLE SEPARATOR--></mo>
         <mn>2</mn>
       </mrow>
     </msub>
   </math>
   <math>
     <mrow>
       <mn>2</mn>
       <mo>&#x2064;<!-- INVISIBLE PLUS --></mo>
       <mfrac>
         <mn>3</mn>
         <mn>4</mn>
       </mfrac>
     </mrow>
   </math>

 </body>
</html>
