Effect of early versus delayed interferon beta-1b treatment on disability after a first clinical event suggestive of multiple sclerosis: a 3-year follow-up analysis of the BENEFIT study. - Kappos L; Freedman MS; Polman CH; Edan G; Hartung HP; Miller DH; Montalbán X; Barkhof F; Radü EW; Bauer L; Dahms S; Lanius V; et al. (Lancet, 2007)