Intramuscular interferon beta-1a therapy initiated during a first demyelinating event in multiple sclerosis. CHAMPS Study Group - Jacobs, LD; Beck, RW; Simon, JH; Kinkel, RP; Brownscheidle, CM; Murray, TJ; Simonian, NA; Slasor, PJ; Sandrock, AW (N Engl J Med, 2000)