@TechReport{ZuendorfSchuerr91,
  author =    {Albert Z\"undorf and Dr. Andreas Sch\"urr},
  title =     "Nondeterministic {C}ontrol {S}tructures for {G}raph {R}ewriting {S}ystems",
  institution = "RWTH Aachen",
  year =      "1991",
  number =    "AIB-17-1991",
  url =       "http://aib.informatik.rwth-aachen.de/1991/1991-17.ps.gz",
}