The effect of an activated prothrombincom-plex concentrate (Feiba) on joint and muscle bleeding in patients with hemophilia A and antibodies to factor VIII. A doubleblind clinical trial - Sjamsoedin, L J M; Heijen, L; Mauser-Bunschoten, E P; van Geijlswijk, J L; van Houwelingen, H; van Asten, P; Sixma, J J (N Engl J Med., 1981)