Voronkov,M.G. et al.
Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1976 , vol. 25, p. 1312 - 1315
Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1976 , vol. 25, # 6 p. 1368 - 1370