1. Liu Chun-Hua, A. S. Pashinkin, and A. V. Novoselova, Dokl. Akad. Nauk SSSR, 151(6): 1335 (1963).
2. H. Spandau and F. Klanberg, Z. Anorg. Chem., 295: 291 (1958).
3. D. Mootz and R. Kunzmann, Acta Cryst., 15: 913 (1962).
4. I. V. Davydov and I. P. Diev, Zh. Neorg. Khim., 2(9): 2003 (1957).
5. A. D. Pogorelyi and N. K. Morozova, Izv. vuzov, Tsvetnaya metallurgiya, No. 4, p. 113(1960).