The Span-Wagner (non-polar and polar) equations of state are described in:

Span, R.; Wanger, W. - Equations of State for Technical Applications. I. Simultaneously Optimized Functional Forms for Nonpolar and Polar Fluids. *Int. J. Thermophys.* **2003**, *24(1)*, 1-39. The two equations differ slightly in their constant parameters.

The specific forms of the **NON-POLAR ** and **POLAR** equations used in *TDE* are given in the **IUPAC ThermoML **data-communication standard.

The article describing the standard is here: *Pure Appl. Chem.* **2006**, *78(3)*, 541-612.

The **POLAR** equation is given on page 71 of the article (page 611 of the* Journal*).

The **NON-POLAR** equation is given on page 70 of the article (page 610 of the* Journal*).

**Equation parameters** are available in several formats from *TDE*: **Equation Parameters in TDE**