1. G. Birkhoff, Hydrodynamics, Princeton UP, 1960.
2. L. V. Ovsjiannikov, Group properties of differential equations, Novosibirsk, 1962.
3. D. V. Alexseevsky, A. M. Vinogradov, V. V. Lychagin, Basic ideas and concepts of differential geometry, Springer, 1991.
4. G. Cicogna, G. Gaeta, Symmetry and perturbation theory in nonlinear dynamics, Springer, 1999.
5. I. S. Krasil'schik, A. M. Vinogradov, Symmetries and conservation laws for differential equations of mathematical physics, A.M.S., 1999.