PRISMS-4: Long-term efficacy of interferon-beta-1a in relapsing MS by Francis, G, Hughes, R, King, J, Mitchell, P, Joubert, J, McLeod, J, Parker, G, Pollard, J, Sindic, C, Duprez, T, Medaer, R, Broeckx, J, Vanroose, E, Carton, H, Wilms, G, Rice, G, Ebers, G, Lee, D, Freedman, M, Nelson, R, Rabinovitch, H, Christie, S, Avruch, L, Oger, J, Paty, D