Biannual radiographic assessments of hands and feet in a three-year prospective follow up of patients with early rheumatoid arthritis. - van der Heijde,D.M.; van Leeuwen,M.A.; van Riel,P.L.; Koster,A.M.; van't Hof,M.A.; van Rijswijk,M.H.; van de Putte,L.B. (Arthritis Rheum, 1992)