The European Spondyloarthropathy Study Group Preliminary Criteria for the Classification of Spondyloarthropathy. - Dougados,M.; Linden,S von der.; Juhlin,R.; Huitfeldt,B.; Amor,B.; Calin,A.; Cats,A.; Dijkmans,B.; Olivieri,I.; Pasero,G.; Veys,E.; Zeidler,H. (Arthritis Rheum, 1991)