1. H. Zellner, US Patent No. 3935214; Chem. Abstr., 85, 214956 (1976).
2. Japanese Patent No. 80136280; Chem. Abstr., 94, 156968 (1981).
3. W. Zumma, et al., US Patent No. 4163849; Chem. Abstr., 92, 41986 (1980).
4. J. Seubert, R. Pohlke, and F. Loeblich, Experientia, 33, 1036 (1977).
5. G. Struve, C. Gazzola, and G. Kenyon, J. Org. Chem., 42, 3069 (1977).