Topological signature of first-order phase transitions in a mean-field model L. Angelani, L. Casetti, M. Pettini, G. Ruocco and F. Zamponi Europhys. Lett., 62 6 (2003) 775-781 Published online: 01 June 2003 DOI: 10.1209/epl/i2003-00439-9