Henry I. Mosberg, Robin Hurst, Victor J. Hruby, James J. Galligan, Thomas F. Burks, Kelvin Gee, Henry I. Yamamura,
[D-Pen2, L-Cys5]enkephalinamide and[D-Pen2, D-Cys5] enkephalinamide, conformationally constrained cyclic enkephalinamide analogs with delta receptor specificity. Biochemical and Biophysical Research Communications. ,vol. 106, pp. 506- 512 ,(1982) ,
10.1016/0006-291X(82)91139-1