1. Burkov, V.I., Neorg. Mater., 1996, vol. 32, no. 12, pp. 1415–1419.
2. Burkov, V.I., Mistryukov, V.E., Mikhailov, Yu.N., and Chuklanova, E.B., Zh. Neorg. Khim., 1997, vol. 42, no. 3, pp. 391–395.
3. Ferrari, A., Nardelli, M., and Tani, M.E., Gazz. Chim. Ital., 1957, vol. 87, pp. 1203–1208.
4. Spitsyn, V.I., Kolesnik, V.V., Mistryukov, V.E., et al., Dokl. Akad. Nauk SSSR, 1983, vol. 273, pp. 355–359.
5. Cambridge Structural Database System, Cambridge Crystallographic Data Centre, 2010.