In mathematics, the Einstein function, named after Albert Einstein, is a name occasionally used for one of these functions.
References
E W Lemmon, R Span, 2006, Short Fundamental Equations of State for 20 Industrial Fluids, J. Chem. Eng. Data 51 (3), 785–850 . Wolfram MathWorld: http://mathworld.wolfram.com/EinsteinFunctions.html