@inproceedings{PODS-2011-Libkin,
	author        = "Leonid Libkin",
	booktitle     = "{Proceedings of the 30th Symposium on Principles of Database Systems}",
	doi           = "10.1145/1989284.1989294",
	isbn          = "978-1-4503-0660-7",
	pages         = "59--70",
	publisher     = "{ACM}",
	title         = "{Incomplete information and certain answers in general data models}",
	year          = 2011,
}