@INPROCEEDINGS{Selikov95,
  author       = {Selikov, A. Z. and Ponomarenko, L. A. and Qranamarenko, L. S. and Zonomarenko, L. U.},
  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},
}