rec-csymbol3

Boltzmann's constant

W3C sample	WIRIS
	$k$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <csymbol encoding="text" definitionURL="www.example.org/universalconstants/Boltzmann.htm">k</csymbol>
</math>

Author: MathML 2 Recomendation