G. Gallavotti, E.G.D. Cohen
Note on nonequilibrium stationary states and entropy
(279K, Postscript)

ABSTRACT.  In transformations between nonequilibrium stationary states, entropy
might be a not well defined concept. It might be analogous to the
``heat content'' in transformations in equilibrium which is not well
defined either, if they are not isochoric ({\it i.e.} do involve
mechanical work). Hence we conjecture that un a nonequilbrium
stationary state the entropy is just a quantity that can be
transferred or created, like heat in equilibrium, but has no physical
meaning as ``entropy content'' as a property of the
system.