Unfractionated heparin inhibits thrombin-catalyzed amplification reactions of coagulation more efficiently than those catalyzed by factor Xa - Ofosu, F A; Hirsh, J; Esmon, C T; Modi, G J; Smith, L M; Anvari, N; Buchanan, M R; Fenton, J W, II; Blajchman, M A (Biochem J, 1989)