@TechReport{StaudtNissenJeusfeld93,
  author =    "M. Staudt and H.W. Nissen and M.A. Jeusfeld",
  title =     "Query by {C}lass, {R}ule and {C}oncept",
  institution = "RWTH Aachen",
  year =      "1993",
  number =    "AIB-15-1993",
  url =       "http://aib.informatik.rwth-aachen.de/1993/1993-15.ps.gz",
}