@article{Arenas:2016:ECF:2936309.2886095,
  title = "The Exact Complexity of the First-Order Logic Definability Problem",
  author = "Arenas, Marcelo and Diaz, Gonzalo I.",
  year = "2016",
  address = "New York, NY, USA",
  issn = "0362-5915",
  journal = "ACM Trans. Database Syst.",
  keywords = "Definability problem, expressiveness, first-order logic, relational algebra",
  month = "may",
  number = "2",
  pages = "13:1--13:14",
  publisher = "ACM",
  url = "http://doi.acm.org/10.1145/2886095",
  volume = "41",
  doi = "10.1145/2886095",
}