J. Borowiec, S. Thelin, L. Bagge, J. van der Linden, E. Thörnö, and H.-E. Hansson, “Heparin-coated cardiopulmonary bypass circuits and 25% reduction of heparin dose in coronary artery surgery—a clinical study”, ujms, vol. 97, no. 1, pp. 55-66, Mar. 1992.