@inproceedings{BaranyTencateOtto2012,
  booktitle = {Proceedings of Very Large Data Bases (PVLDB), 2012},
  year = {2012},
  author = {Barany, Vince and ten Cate, Balder and Otto, Martin},
  title = {Queries with guarded negation},
  pages = {1328-1339},
}