@TechReport{KoenigRiesHelmerMoerkotte95,
  author =    {K\"onig-Ries,Birgitta and Helmer, Sven and Moerkotte,Guido},
  title =     "An experimental study on the complexity of left-deep join ordering problems for cyclic queries",
  institution = "RWTH Aachen",
  year =      "1995",
  number =    "AIB-04-1995",
  url =       "http://aib.informatik.rwth-aachen.de/1995/1995-04.ps.gz",
}