Evidence for a glassy dynamics in (Rb-NH4)2SO4 mixed compounds D. De Sousa Meneses, P. Simon, G. Hauret and M. Maglione Europhys. Lett., 36 6 (1996) 461-466 Published online: 01 September 2002 DOI: 10.1209/epl/i1996-00252-0