1. A.A. Borovkov,Random Processes in Queueing Theory (Hayka, Mackba, 1972, in Russian) [English Transi.: Springer, Berlin, Heidelberg, New York, 1976].
2. A.A. Borovkov, Continuity theorems for multichannel systems with losses, Teop. Report, IPHMEH 17(1972)458–468, in Russian.
3. A. Brandt, On stationary queue length distributions for G/M/S/r queues, Queueing Systems 2(1987)321–332.
4. A.K. Erlang, Solution of some problems in the theory of probabilities of significance in automatic telephone exchanges, Electroteknikeren 13(1917)5–13, in Danish [English transl. in: P.O. Elec. Eng. J. 10(1917–18)189–197.
5. P. Franken, Beitrage zur Bedienungstheorie, Habilitationsschrift, Friedrich-Schiller-University Jen (1969), in German.