@TechReport{BurkartSteffen92,
  author =    "Olaf Burkart and Bernhard Steffen",
  title =     "Model {C}hecking for {C}ontext-{F}ree {P}rocesses",
  institution = "RWTH Aachen",
  year =      "1992",
  number =    "AIB-06-1992",
  url =       "http://aib.informatik.rwth-aachen.de/1992/1992-06.ps.gz",
}