The constant $\textit{Molar Gas Constant}$, also known as the gas constant, universal, or ideal gas constant, denoted by the symbol $R$,
is a physical constant which is featured in many fundamental equations in the physical sciences,
such as the ideal gas law and the Nernst equation.
It is equivalent to the Boltzmann constant, but expressed in units of energy (i.e. the pressure-volume
product) per temperature increment per mole (rather than energy per temperature increment per particle).
http://physics.nist.gov/cuu/Constants/bibliography.html
http://en.wikipedia.org/wiki/Gas_constant
http://dbpedia.org/resource/Gas_constant
$pV_m = RT$, where $p$ is pressure, $V_m$ is molar volume, and $T$ is thermodynamic temperature.
http://www.iso.org/iso/catalogue_detail?csnumber=31894
http://www.iso.org/iso/catalogue_detail?csnumber=31894