@inproceedings{PODS-2010-DavidLM,
	author        = "Claire David and Leonid Libkin and Filip Murlak",
	booktitle     = "{Proceedings of the 29th Symposium on Principles of Database Systems}",
	doi           = "10.1145/1807085.1807112",
	isbn          = "978-1-4503-0033-9",
	pages         = "191--202",
	publisher     = "{ACM}",
	title         = "{Certain answers for XML queries}",
	year          = 2010,
}