1. I. I. Vol'nov, S. A. Tokareva, V. N. Belevskii, and E. I. Latysheva, Izv. Akad. Nauk SSSR, Ser. Khim., No. 10, 2365 (1968).
2. A. B. Tsentsiper, et al., Zh. Neorgan. Khim.,4, 1952 (1959).
3. N. G. Vannerberg, Arkiv Kemi,14, 99 (1959).
4. L. I. Mirkin, Source Book on the X-Ray Structural Analysis of Polycrystalline Materials [in Russian], Fizmatgiz, Moscow (1961).