@InProceedings{Hier03:cmcs,
  author =   {F. Bartels and A. Sokolova and Vink, E.P. de},
  title =    {A hierarchy of probabilistic system types},
  booktitle =    {Proc.\ CMCS'03},
  series = {ENTCS},
  volume = {82},
  year =     2003,
  editor =   {H. P. Gumm},
}