1. Smith, R., Impulsive Differential Equations with Applications to Self-Cycling ermentation, Hamilton: MacMaster Univ., 2001 http://diggitalcommons.master.ca/opendissertation/1526).
2. Larin, V.B., Upravlenie shagayushchimi apparatami (Control overWalking Mechanisms), Kiev: Naukova Dumka, 1980.
3. Lyapunov, A.M., Obshchaya zadacha ob ustoichivosti dvizheniya (General Problem of Motion Stability), Moscow: Gostekhizdat, 1950.
4. Khazin, L.G. and Shnol’, E.E., Ustoichivost’ kriticheskikh polozhenii ravnovesiya (Stability of Critical Equilibria), Pushchino: NTsBI AN SSSR, 1985.
5. Martynyuk, A.A. and Obolenskii, A.Yu., A Study of Stability of Autonomous Comparison Systems, Preprint of Inst. of Mathematics, USSR Acad. Sci., Kiev, 1978, no. 78.28.