Van Kampen's expansion approach in an opinion formation model M. S. de la Lama, I. G. Szendro, J. R. Iglesias and H. S. Wio Eur. Phys. J. B, 58 2 (2007) 221 Published online: 01 August 2007 DOI: 10.1140/epjb/e2007-00206-4