Second law of thermodynamics
The second law of thermodynamics may be expressed in many specific ways, the most prominent classical statements being the statement by Rudolf Clausius (1854), the statement by Lord Kelvin (1851), and the statement in axiomatic thermodynamics by Constantin Carathéodory (1909). These statements cast the law in general physical terms citing the impossibility of certain processes. The Clausius and the Kelvin statements have been shown to be equivalent.
Herbert Callen
Herbert Bernard Callen (1919 – May 22, 1993) was an American physicist best known as the author of the textbook "Thermodynamics and an Introduction to Thermostatistics", the most frequently cited thermodynamic reference in physics research literature. During World War II he was also called upon to undertake theoretical studies of the principles underpinning the effort to create the atom bomb.