1. Samsonov, G. V., Serebryakova, T. I., Neronov, V. A.: Boridy, Moskva Atomizdat, 1975.
2. Berezin, A. A., Golikova, O. A., Zaitsev, V. R., Kazanin, M. M., Orlov, V. M., Tkalenko, E. N., in:Boron and Refractory Borides, (Matkovich V. I., ed.) Springer: Berlin, Heidelberg, New York 1977, p. 52.
3. Lundström, T.: see [77B], p. 351.
4. Armstrong, D. R.: Proc. 7th Int. Symp. Boron, Borides and Related Compounds. Uppsala, Sweden, 1981; spec. issue of J. Less-Common Met. 82 (1981) 357.
5. Hiebl, K., Rogl, P., Sienko, M.J.: J. Less-Common Met. 82 (1981) 201.