1. 1) T. Goto, J. Li and T. Hirai: J. Jpn. Soc. Powder and Powder Metallurgy, 43 (1996), 306.
2. 2) C. Wood: Novel Refractory Semiconductor, Mat. Res. Soc. Symp. Proc., Vol. 97, ed. by D. Emin, T. L. Aselage and C. Wood, Materials Research Society, Pittsburgh, (1987), p. 335.
3. 3) C. Wood: Boron-rich Solid, AIP Conf. Proc., Vol. 140, ed. by D. Emin, T. L. Aselage, C. L. Beckel, I. A. Howard and C. Wood, American Institute of Physics, New York, (1986), p. 206.
4. 4) K. Koumoto: Amer. Ceram. Soc. Bull., 73 No. 10 (1994), 84.
5. 5) T. L. Aselage, D. Emin, C. Wood, I. Mackinnon and I. Howard: Novel Refractory Semiconductor, Mat. Res. Soc. Symp. Proc., Vol. 97, ed. by D. Emin, T. L. Aselage and C. Wood, Materials Research Society, Pittsburgh, (1987), p. 27.