Vints,V.V. et al. Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1973 , vol. 22, p. 1507 - 1511 Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1973 , vol. 22, # 7 p. 1555 - 1559