Two independent alleles at 6q23 associated with risk of rheumatoid arthritis - Plenge, RM; Cotsapas, C; Davies, L; Price, AL; Bakker, PIW; Maller, J; Pe'er, I; Burtt, NP; Blumenstiel, B; DeFelice, M; Parkin, M; Barry, R; et al. (Nature genetics, 2007)