M.A. Ondetti, J. Pluscec, E.F. Sabo, J.T. Sheehan, and N. Williams, J. Am. Chem. Soc., 92, 195 (1970). (Chem. Synthesis)

J.E. Jorpes and V. Mutt (eds.) Secretin, Cholecystokinin, Pancreozymin and Gastrin, Handbook of Experimental Pharmacology, Vol. 34, Springer-Verlag, Berlin, 1973. (Review)