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