1. Bailey EI, Harper TA, Pinkertin PH. The “therapeutic range” of the one-stage Prothrombin time in the control of anticoagulant therapy: the effect of different thromboplastin preparations. Canad Med Ass J 1971; 105: 1041–1044.
2. Bain B, Forster T, Sleigh B. Control of oral anticoagulants by the Prothrombin time: a plea for uniformity. Aust Med J 1978; 2: 459–461.
3. Bradlow BA, Saunder C, Whitbread P et al. Standardisation of the laboratory control of anticoagulant therapy. SA Med J 1974; 48: 1857–1862.
4. Brink S, Cloete H, Roberts R, Holm W. Laboratoriumstandaardisasie en kwaliteitscontrole in antistolterapie. SA Med J 1976; 50: 205–208.
5. Ingram GIC. The stability of the WHO reference thromboplastin NIBS&C 67/40. Thromb Haemostas 1979; 42: 1135–1140.