1. V. M. Alekseev, V. M. Tikhomirov, and S. V. Fomin, Optimal Control [in Russian], Fizmatlit, Moscow (2005).
2. G. I. Arkhipov, V. A. Sadovnichy, and V. N. Chubarikov, Lecture on Mathematical Analysis [in Russian], Dropha, Moscow (2003).
3. V. L. Bakke, “Optimal fields of problems with delays,” J. Optim. Theory Appl., 33, No. 1, 69–84 (1981).
4. D. H. Chyung and E. B. Lee, “Linear optimal systems with time delays,” SIAM J. Control, 4, No. 3, 548–575 (1966).
5. L. E. Elsgolts and S. B. Norkin, Introduction to Theory of Differential Equations with Decelerating Parameter [in Russian], Nauka, Moscow (1971).