1. Cooper, R. B., Introductionto Queueing Theory, 2nd ed.North-Holland, Amsterdam, 1981, pp.178-185.
2. Tijms, H. C., Stochastic Models: An Algorithmic Approach, Wiley, New York 1994, pp.288-292.
3. Hoel, P. G., Port, S. C., and Stone, C. J., Introduction to Stochastic Processes, Waveland Press, Prospect Heights, IL, 1987, pp.84-110.