Dzhemilev,U.M. et al. Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1979 , vol. 28, p. 2512 - 2516 Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1979 , vol. 28, # 12 p. 2702 - 2706