1. A. V. Kim, Lyapunov’s Second Method in the Theory of Stability of Hereditary Systems [in Russian], Izd. Ural. Gos. Univ., Yekaterinburg (1992).
2. N. N. Krasovskii, Some Problems in the Theory of Stability of Motion [in Russian], Fizmatgiz, Moscow (1959).
3. V. Yu. Slyusarchuk, Absolute Stability of Dynamic Systems with Aftereffect [in Ukrainian], Ukr. Derzh. Univ. Vod. Gosp. Prirodokoryst., Rivne (2003).
4. J. K. Hale, Theory of Functional Differential Equations, Springer-Verlag, New York–Heidelberg–Berlin (1977).
5. D. Ya. Khusainov and A. V. Shatyrko, Method of Lyapunov Functions in Stability Analysis of Functional Differential Systems [in Russian], Izd. Kyiv. Univ., Kyiv (1997).