IUBMB 1972: IUBMB Enzyme Nomenclature [Internet]. London (GB): Queen Mary, University of London [chymotrypsin: CAS 9004-07-3, EC 3.4.21.1 created 1961 as EC 3.4.4.5 and EC 3.4.4.6, transferred 1972 to EC 3.4.21.1; Accessed 2012 March 28]. Available from: http://www.chem.qmul.ac.uk/iubmb/enzyme/EC3/4/21/1.html