The effect of activated prothrombin-complex concentrate (FEIBA) on joint and muscle bleeding in patients with hemophilia A and antibodies to factor VIII. A double-blind clinical trial - Sjamsoedin, LJM; Heijnen, L; Mauser-Bunschoten, EP; van Geijlswijk, JL; van Houwelingen, H; van Asten, P; Sixma, JJ (N Engl J Med, 1981)