1. S. Asmussen,Applied Probability and Queues (Wiley, 1987).
2. S. Asmussen and S. Foss, Renovation, regeneration and coupling in multi-server queues in continuous time, Preprint No. 1990-2, Dept. of Math., Chalmers Univ. of Technology, The University of Göteborg (1990), to appear in Ann. Appl. Prob.
3. A. Borovkov,Asymptotic Methods in Queueing Theory (Nauka, Moscow, 1980) (in Russian). (English translation: Wiley, 1984).
4. A. Borovkov, Limit theorems for queueing networks I, Theory Prob. Appl. 31 (1986) 474–490.
5. S. Foss, On conditions of ergodicity for multi-server queues, Sibirsk. Math. Zhurnal 24 (1983) 168–175 (in Russian).