Generalization of a nonlinear friction relation for a dimer sliding on a periodic substrate M. Tiwari, S. Gonçalves and V. M. Kenkre Eur. Phys. J. B, 62 4 (2008) 459-464 Published online: 22 May 2008 DOI: 10.1140/epjb/e2008-00194-9