Dyachenko, V. I.; Galakhov, M. V.; Kolomiets, A. F.; Fokin, A. V.
Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1988 , vol. 37, # 5 p. 1056
Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1988 , # 5 p. 1196

Mustafa, Mohamed El-said; Takaoka, Akio; Ishikawa, Nobuo
Heterocycles, 1986 , vol. 24, # 3 p. 593 - 599