Etanercept treatment of psoriatic arthritis: safety, efficacy, and effect on disease progression. - Mease,P.J.; Kivitz,A.J.; Burch,F.X.; Siegel,E.L.; Cohen,S.B.; Ory,P.; Salonen,D.; Rubenstein,J.; Sharp,J.T.; Tsuji,W. (Arthritis Rheum, 2004)