Gurami Tsitsiashvili M. A. Osipova N. V. Koliev Dieter Baum A Product Theorem for Markov Chains with Application to PF-Queueing Networks. 141-154 2002 113 Annals OR 1-4 http://dx.doi.org/10.1023/A:1020914029651 db/journals/anor/anor113.html#TsitsiashviliOKB02