@article{journals/jacm/GottlobLS01,
  title = "The complexity of acyclic conjunctive queries",
  author = "Georg Gottlob and Nicola Leone and Francesco Scarcello",
  year = "2001",
  journal = "J. {ACM}",
  number = "3",
  pages = "431-498",
  url = "10.1145/382780.382783",
  volume = "48",
}