Contrasting behaviour of acoustic modes in network and non-network glasses A. Matic, L. Börjesson, G. Ruocco, C. Masciovecchio, A. Mermet, F. Sette and R. Verbeni Europhys. Lett., 54 1 (2001) 77-83 Published online: 01 December 2003 DOI: 10.1209/epl/i2001-00231-y