1. Akira Yamakawa and Shinya Oka: Japan, Japn Kokai Tokkyo Koho JP0226872. 1990-1-29.
2. Tetsuga Abe, Yoshio Murakami: Japan, Japn Kokai Tokkyo Koho JPD2224402. 1990-09-06.
3. G. Suchanek, Y. M. Tairov and V. F. Tsveikov: Sov. Tech. Phys. Lett. Vol. 9(1983), p.31.
4. A. P. Dmitriev, N. V. Evlakhov, and A. S. Furman: Semiconductors Vol. 30(1996), p.60.
5. Wenbo Bu, Tai Qiu, et al.: Key Engineering Materials vol. 247(2003), p.111.