@INPROCEEDINGS{Melikov95, author = {Melikov, A. Z. and Ponomarenko, L. A.}, title = {On the approach to optimal control of queuing systems with multiple classes of customers}, booktitle = {Proc.\ International Conf.\ on Syst.\ Sci.\ XII.}, address = {Wroclaw (Poland)}, year = {1995}, pages = {507-515}, }