1. JP Pat. 63192727, 1988.
2. N. Yoshihiro, K. Masahiko, Kawasaki Steel Techn. Rept., 1990, 23, 65.
3. US Pat. 20040242441, 2004.
4. Pat. RF 2147022, Byul. Izobr. [Invention Bulletin], 2000, No. 6 (in Russian).
5. M. Sawamoto, T. Masuda, H. Nischii, T. Higashimura, J. Polym. Sci., 1975, 13, 279.