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2. A. Ya. Bulgakov and S. K. Godunov, ?The stability property of a system of linear differential equations with constant coefficients, and its numerical estimate,? Preprint No. 51, Computing Center, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk (1978).
3. V. D. Furasov, Stability of Motion, Estimates and Stabilization [in Russian], Nauka, Moscow (1977).
4. A. Kh. Gelig, G. A. Leonov, and V. A. Yakubovich, Stability of Nonlinear Systems with Nonunique State of Equilibrium [in Russian], Nauka, Moscow (1978).
5. E. A. Barbashin, Lyapunov Functions [in Russian], Nauka, Moscow (1970).