1. G. P. Klimov, Stochastic Queuing Systems [in Russian], Nauka, Moscow (1966).
2. L. Takács, “On Erlang’s formula,” Ann. Math. Stat., Vol. 40, No 1, 71–78 (1969).
3. D. König and D. Stoyan, Methoden der Bedienungstheorie, Akademie-Verlag, Berlin (1976).
4. T. Saati, Elements of Queuing Theory and Its Applications [Russian translation], Librocom, Moscow (2010).
5. B. V. Gnedenko and I. N. Kovalenko, Introduction to Queuing Theory [in Russian], LKI, Moscow (2012).