1. Lyapunov, A. M.:The General Problem of the Stability of Motion, Kharkov, 1892. French translation inAnn. Fac. Sci. Toulouse 9 (1907), 203?474. Republished by Princeton University Press, 1947.
2. Poincaré, H.: Memoire sur les corbes définies par les equations differentielles,J. Math. Pures Appl. Sér. 4,2 (1886).
3. Zhukovskij, N. E.: On solidity of motion, inCollection of Works, Vol. 1, pp. 67?161, Gostekhizdat, Moscow, Leningrad, 1948. First editionUchjenye Zapiski Moskovskogo Universiteta, No. 4, 1882.
4. Rouche, N., Habets, P., and Laloy, M.:Stability Theory by Lyapunov's Direct Method, Springer, New York, Heidelberg, Berlin, 1977.
5. Matrosov, V. M.: Comparison method in system's dynamics, in P. Janssens, J. Mawhin, and N. Rouche (eds),Equations différentielles et fonctionnelles non linéaires, Hermann, Paris, 1973, pp. 407?445.