1. Sergeev, V.A., Shitikov, V.K., Abbasov, G.U., Bairamov, M.R., and Zhdanov, A.A., Vysokomol. Soedin., A, 1987, vol. 29, p. 2441.
2. US Patent no. 4923912, 1990.
3. JP Patent no. 63199220, 1988.
4. RF Patent no. 2211845, 2001.
5. Germany Patent no. 937555, 1956.