Comparison by controlled clincial trial of streptokinase and heparin in treatment of life-threatening pulmonary embolism - Tibbutt, D A; Davies, J A; Anderson, J A; Fletcher, E W L; Hamill, J; Holt, J M; Thomas, M L; Lee, G J; Miller, G A H; Sharp, A A; Sutton, G C (British Medical Journal, 1974)