Usar, I. Ya., I. A. Makushenko, and Iu. O. Protopop. 2020. “The Convergense Rate of Stationary Distribution of Retrial Queueing System With Queue”. Bulletin of Taras Shevchenko National University of Kyiv. Physics and Mathematics, no. 3 (February): 52-55. https://doi.org/10.17721/1812-5409.2019/3.7.