1. USSR Inventor's Certificate 129936; Byull. Izobret., No. 3, (1960).
2. USSR Inventor's Certificate 348549; Otkritiya, No. 25 (1972).
3. USSR Inventor's Certificate 365354; Otkritiya, No. 6 (1973).
4. USSR Inventor's Certificate 303870; Otkritiya, No. 47 (1975).
5. USSR Inventor's Certificate 521267; Otkritiya, No. 26 (1976).