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2. A. Berman and R. J. Plemmons, Nonnegative Matrices in the Mathematical Sciences (Academic Press, New York, 1979).
3. G. V. Demidenko and I. I. Matveeva, “Stability of solutions to delay differential equations with periodic coefficients of linear terms,” Sib. Mat. Zh. 48, 1025 (2007) [Sib. Math. J. 48, 824 (2007)].
4. B. P. Demidovich, Lectures on Mathematical Stability Theory (Nauka, Moscow, 1967) [in Russian].
5. L. E. El’sgol’ts and S. B. Norkin, Introduction to the Theory and Application of Differential Equations with Deviating Arguments (Nauka, Moscow, 1971; Academic Press, New York-London, 1973).