Vorob'eva,E.A. et al. Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1974 , vol. 23, p. 2734 - 2736 Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1974 , vol. 23, # 12 p. 2832 - 2834