1. Makimoto, K., Sekimoto, M., Fujikake, S., and Ishii, M.European Patent 0649818 A1, 1994.
2. Konstantinov, K., Zhong, S., Wang, C., Liu, H., and Dou, S.Australian Patent 2002100001 A4, 2002.
3. Shin, D. Y.U.S. Patent 5 587 139, 1996.
4. Shin, D. Y.U.S. Patent 5 498 403, 1996.
5. Ikoma, M., Akutsu, N., Enokido, M., Yoshii, F., Kaiya, H., and Tsuda, S.U.S. Patent 5 700 596, 1997.