1. L. Berezansky and E. Braverman, “On Existence of Positive Solutions for Linear Difference Equations with Several Delays,” Adv. Dynam. Systems Appl. 1(1), 29–47 (2006).
2. S. Elaydi, “Periodicity and Stability of Linear Volterra Difference Systems,” J. Math. Anal. Appl. 181(2), 483–492 (1994).
3. N. V. Azbelev, V. P. Maksimov, and L. F. Rakhmatullina, Introduction to the Theory of Functional Differential Equations (Nauka, Moscow, 1991) [in Russian].
4. A. D. Myshkis, Linear Differential Equations with Delayed Argument (Nauka, Moscow, 1972) [in Russian].
5. V. V. Malygina, “Several Stability Criteria for Equations with Delayed Argument,” Differents. Uravneniya 28(10), 1716–1723 (1992).