Stepanov,M.V. et al. Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1975 , vol. 24, p. 2430 - 2433 Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1975 , vol. 24, # 11 p. 2544 - 2547