1. G. V. Samsonov, L. Ya. Markovskii, A. F. Zhigach, and M. G. Valyashko, Boron, Its Compounds and Alloys [in Russian], Izd-vo AN USSR, Kiev (1960).
2. K. I. Portnoi, M. Kh. Levinskaya, and V. M. Romashov, Poroshkovaya Met., No. 8, 66 (1969).
3. A. P. Ostranitsa, G. V. Samsonov, and V. S. Sinel'nikova, Information Letter No. 127 [in Russian], IMSS AN USSR (1958).
4. V. A. Yupko, Zavod. Lab.,35, No. 6 (1969).
5. T. S. Verkhoglyadova, Information Letter No. 88 [in Russian], IMSS AN USSR (1955).