1. P. J. Olver, Applications of Lie Groups to Differential Equations, Springer (1986).
2. E. B. Vinberg and V. L. Popov, “Theory of invariants,” in: VINITI Series in Contemporary Problems of Mathematics. Fundamental Trends [in Russian], Vol. 55, VINITI, Moscow (1989), pp. 137–309.
3. D. V. Alekseevskii, A. M. Vinogradov, and V. V. Lychagin, “Fundamental ideas and concepts of differential geometry,” in: VINITI Series in Contemporary Problems of Mathematics. Fundamental Trends,Vol. 28, VINITI (1988), pp. 5–298.
4. L. S. Pontryagin, Continuous Groups [in Russian], Nauka, Moscow (1984).
5. A. M. Samoilenko and N. A. Perestyuk, Impulsive Differential Equations [in Russian], Vyshcha Shkola, Kiev (1987).