1. Q. V. Samsonov, L. Ja. Markovskii, A. F. Zhigach, and M. G. Valjashko, “Bor, ego soedinenija i splavi” (Izd vo AN USSR, Kiev, 1960).
2. B. F. Decker and J. S. Kasber, Acta Crystallogr 12 (1959) 503.
3. W. Klein and D. Geist, Z. Physik 201 (1967) 411.
4. D. Geist, J. Meyer and H. Peussner, “Boron-Preparation and Properties”, Vol. 3, Proceedings of the International Symposium on Boron, Warsaw (1968) p. 213.
5. J. J. Koulmann, N. Perol and P. Taglang, Compt. Rend. 267 (1368) B15.