@inproceedings{conf/focs/GottlobKS00,
  title = "Existential Second-Order Logic over Graphs: Charting the Tractability Frontier",
  author = "Georg Gottlob and Phokion G. Kolaitis and Thomas Schwentick",
  year = "2000",
  booktitle = "{FOCS}",
  pages = "664-674",
}