@inproceedings{PODS-1994-ParedaensBG,
	author        = "Jan Paredaens and Jan Van den Bussche and Dirk Van Gucht",
	booktitle     = "{Proceedings of the 13th Symposium on Principles of Database Systems}",
	doi           = "10.1145/182591.182640",
	isbn          = "0-89791-642-5",
	pages         = "279--288",
	publisher     = "{ACM Press}",
	title         = "{Towards a Theory of Spatial Database Queries}",
	year          = 1994,
}