invChars

Many ways of not printing anything.

W3C sample	WIRIS
	$\mathrm{}\mathrm{}\text{}$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mn/>
  <mo/>
  <mi> </mi>
  <mo>&#x2062;</mo>
  <mn>&#x0009;</mn>
  <mo>&#x2061;</mo>
  <mtext> &#x200B; </mtext>
</math>

Author: Dave Doyle, Design Science