Conformational aspects of beta-trypsin interaction with substrates and pancreatic trypsin inhibitor. I. Conformational properties of residues in the enzyme-active center and the structure of a non-valent enzyme-substrate complex Godzhaev, N.M.; Aliev, R.E.; Popov, E.M. Molekuliarnaia Biologiia 20(1): 102-119 1986 https://eurekamag.com/research/039/660/039660205.php