Thermodynamics. Using Affinities to define reversible processes
  In this article a definition of reversible processes in terms of differences in intensive Thermodynamics properties (Affinities) is proposed. This definition makes it possible to both define reversible processes before introducing the concept of entropy and avoid the circularity problem that follows from the Clausius definition of entropy changes. The convenience of this new definition compared to those commonly found in textbooks is demonstrated with examples. 
Hern\'an A. Ritacco
physics.class-ph cond-mat.stat-mech