@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",
}