Zav'yalov, S. I.; Knyaz'kova, N. E. Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1980 , vol. 29, p. 1659 - 1662 Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1980 , # 10 p. 2343 - 2346