@TechReport{BurkartSteffen93,
  author =    "Olaf Burkart and Bernhard Steffen",
  title =     "Pushdown {P}rocesses: {P}arallel {C}omposition and {M}odel {C}hecking",
  institution = "RWTH Aachen",
  year =      "1993",
  number =    "AIB-10-1993",
  url =       "http://aib.informatik.rwth-aachen.de/1993/1993-10.ps.gz",
}