Pudovik,M.A. et al. Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1976 , vol. 25, # 12 p. 2648 - 2650 Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1976 , vol. 25, p. 2837 - 2839