Barkhayev, P. Yu., R. Rabah, and G. M. Sklyar. “On the Problem of Exact Controllability of Neutral Systems With Time Delay”. Ukrains’kyi Matematychnyi Zhurnal 68, no. 6 (June 25, 2016): 800–815. Accessed April 11, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/1879.