1. A.S. 172738 (USSR). Otkrytiya, Izobret., Prom. Obraztsy, Tovamye Znaki, No. 14, (1965).
2. A.S. 380649 (USSR), Ibid., No. 22 (1973).
3. A.S. 389086 (USSR), Ibid., No. 29 (1973).
4. A.S. 415971 (USSR), Ibid., No. 197 (1973).
5. A.S. 435232 (USSR), Ibid., No. 25 (1974).