Lenalidomide plus dexamethasone for relapsed multiple myeloma in North America. - Weber DM; Chen C; Niesvizky R; Wang M; Belch A; Stadtmauer EA; Siegel D; Borrello I; Rajkumar SV; Chanan-Khan AA; Lonial S; Yu Z; et al. (New England Journal of Medicine, 2007)