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2. B. P. Demidovich, Lectures on the Mathematical Theory of Stability [in Russian], Nauka, Moscow (1967).
3. L. V. Kantorovich and V. I. Krylov, Approximate Methods of Higher Analysis [in Russian], Gostekhizdat, Moscow-Leningrad (1952).
4. P. Lancaster, Theory of Matrices, Acad. Press, New York (1969).
5. A. M. Lyapunov, The General Problem of the Stability of Motion, Taylor & Francis, London (1992).