Information Technologies and Mathematical Modelling. Queueing Theory and Applications 18th International Conference, ITMM 2019, Named after A.F. Terpugov, Saratov, Russia, June 26-30, 2019, Revised Selected Papers - Dudin, Alexander; Dudin, Alexander; Nazarov, Anatoly; Nazarov, Anatoly; Moiseev, Alexander; Moiseev, Alexander (Springer International Publishing : Imprint: Springer, 2019)