1. B. V. Gnedenko and I. N. Kovalenko, Introduction to Queuing Theory [in Russian], Nauka, Moscow (1966).
2. T. L. Saaty, Elements of Queuing Theory, McGraw-Hill, New York (1961).
3. A. Ya. Khinchin, Works on Mathematical Queuing Theory [in Russian], Fizmatgiz, Moscow (1963).