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Stability Theory of Dynamical Systems. Springer-Verlag, Berlin-Heidelberg-New York 1970.
MR 0289890
[2] J. Kurzweil: On the inversion of Lyapunov's second theorem on stability of motion. Czechoslovak Math. J. 81 (1956), 217-259, 455-473 (in Russian; Summary in English, ibidem, 474-484). English transl.: Amer. Math. Soc. Transl., Ser. II, 24 (1963), 19-77.
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MR 0132259
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[7] V. I. Zubov:
Methods of A. M. Lyapunov and their Application. Leningrad 1957 (in Russian). English transl.: Groningen 1964.
MR 0086966