@inproceedings{PODS-2009-DeHaan,
	author        = "David DeHaan",
	booktitle     = "{Proceedings of the 28th Symposium on Principles of Database Systems}",
	doi           = "10.1145/1559795.1559828",
	isbn          = "978-1-60558-553-6",
	pages         = "207--216",
	publisher     = "{ACM}",
	title         = "{Equivalence of nested queries with mixed semantics}",
	year          = 2009,
}