Thould A K, 1966, Ann Rheum Dis, 25, 220, 10.1136/ard.25.3.220
Brook A, 1977, Ann Rheum Dis, 36, 71, 10.1136/ard.36.1.71
Isomäki H, 1988, Arthritis Rheum, 31, 1452, 10.1002/art.1780311120
Arnett F C, 1988, Arthritis Rheum, 31, 315, 10.1002/art.1780310302