References
- Stahl , G. L. , Walter , R. and Smith , C. W. 1979 . J. Amer. Chem. Soc. , 101 : 5383 – 94 .
- Brt. Pat. 905,186 . September 5, 1962 . American Cyanamid Co.
- Skinner , W. A. , Lange , J. , Shellenberger , T. E. and Colwell , W. T. 1967 . J. Med. Chem. , 10 : 949 – 50 .