Equilibrium thermodynamics and thermodynamic processes in nonlinear systems V. N. Likhachev, T. Yu. Astakhova, W. Ebeling and G. A. Vinogradov Eur. Phys. J. B, 72 2 (2009) 247-256 Published online: 26 September 2009 DOI: 10.1140/epjb/e2009-00317-x