@inproceedings{conf/focs/GottlobLS98,
  title = "The Complexity of Acyclic Conjunctive Queries",
  author = "Georg Gottlob and Nicola Leone and Francesco Scarcello",
  year = "1998",
  booktitle = "{FOCS}",
  pages = "706-715",
  url = "http://computer.org/conferen/proceed/focs/9172/91720706abs.htm",
}