$//<![CDATA[ \begin{array}{l}\displaystyle R_s =\left[ \gamma_g^{c_3} \cdot ( p/c_1 - c_4)\cdot 10^{-X} \right] ^{1/{c_2}}\end{array} //]]>$, $//<![CDATA[ \begin{array}{l}X = c_5 \, T^{c_6} + c_7 \, \gamma_{API}^{c_8}\end{array} //]]>$

$//<![CDATA[ \begin{array}{l}c_1 = 112.727, \ c_2 = 0.5774, \ c_3 = 0.8439, \ c_4 = -12.340\end{array} //]]>$

$//<![CDATA[ \begin{array}{l}c_5 = 4.561 \cdot 10^{-5}, \ c_6 = 1.3911, \ c_7 = -7.916 \cdot 10^{-4}, \ c_8 = 1.5410\end{array} //]]>$