@techreport{3960,
  title = "A general Datalog-based framework for tractable query answering over ontologies",
  author = "Andrea Cal\`{i} and Georg Gottlob and Thomas Lukasiewicz",
  year = "2012",
  institution = "OUCL",
  month = "March",
  number = "RR-10-21",
  pages = "60",
}