Chen Z, Li Y, Mulichak AM, Lewis SD, Shafer JA. Crystal structure of human alpha-thrombin complexed with hirugen and p-amidinophenylpyruvate at 1.6 A resolution. Arch Biochem Biophys. 1995 Sep 10;322(1):198–203. doi: 10.1006/abbi.1995.1452. PMID: 7574675.