http://johncarlosbaez.wordpress.com/2012/01/23/classical-mechanics-versus-thermodynamics-part-2/
http://qed.princeton.edu/main/PlasmaWiki/Thermodynamic_Potentials
http://en.wikipedia.org/wiki/Thermodynamic_potential
http://en.wikipedia.org/wiki/Maxwell_relations
[*7.80]
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