title: The natural history of ankylosing spondylitis: is the disease really changing?
authors: Department of Medicine, Stanford University School of Medicine, CA 94305.
authors: J F
authors: JF
authors: Fries
authors: G
authors: G
authors: Singh
authors: D A
authors: DA
authors: Bloch
authors: A
authors: A
authors: Calin
mesh_terms: D015331:Cohort Studies; D003430:Cross-Sectional Studies; D006801:Humans; D012107:Research Design / Q000592:standards*; D013167:Spondylitis, Ankylosing / Q000503:physiopathology*