1. T. Yoshida, S. Shindo, T. Ogaki, and K. Yamanaka, in “Kaimen-kasseizai Handbook” (in Japanese), New Ed., Kogakutosho, Tokyo, 1978, p. 234.
2. Y. Kawase, T. Sunagoshi, T. Yamaguchi, T. Miura, and K. Iwamura, in “Sekiyu Seisei Gijutsu Binran” (in Japanese), 3rd Ed., Sangyo Tosho, Tokyo, 1981, p. 5.