Natalizumab plus interferon beta-1a for relapsing multiple sclerosis. - Rudick RA; Stuart WH; Calabresi PA; Confavreux C; Galetta SL; Radue E; Lublin FD; Weinstock-Guttman B; Wynn DR; Lynn F; Panzara MA; Sandrock AW; et al. (New England Journal of Medicine, 2006)