1. Assaf, D., Langberg, N.A., Savits, T.H. and Shaked, M., Multivariate Phase-type Distributions,Oper. Res.,32 (1984), 688–702.
2. Chen, B.Q., Ergodicity of the Queueing Model in Seaport,J. Engin. Math.,5(1) (1988), 1–8 (in Chinese).
3. Hsu, G.H., Stochastic Service Systems, 2nd Ed., Science Press, Beijing, 1988.
4. Hsu, G.H. and He, Q.M., The Distribution of the First Passage Time for the Markov Processes of GI/M/1 Type,Stochastic Models,7 (1991), 397–417.
5. Hsu, G.H., He, Q.M. and Liu, X.S., The Stationary Behaviour of Matched Queueing Systems,Acta Math. Appl. Sinica,13 (1990), 31–40 (in Chinese).