1. I. Yoshida andS. Mukai,Kagaku Kogyo 34 (1981) 36.
2. Japanese patents 52-28501 (1977); 55-014387 (1980); 55-113606 (1980).
3. M. Kakuta, in ?An Introduction to Carbon? (Carbon Society of Japan, 1984) p. 116.
4. S. Kiyono,ibid. p. 138.
5. I. Mochida andH. Marsh,TANSO 126 (1986) 89.