@inproceedings{PODS-2004-GottlobKS,
	author        = "Georg Gottlob and Christoph Koch and Klaus U. Schulz",
	booktitle     = "{Proceedings of the 23rd Symposium on Principles of Database Systems}",
	doi           = "10.1145/1055558.1055585",
	ee            = "http://www.acm.org/sigmod/pods/proc04/pdf/P-19.pdf",
	isbn          = "1-58113-858-X",
	pages         = "189--200",
	publisher     = "{ACM}",
	title         = "{Conjunctive Queries over Trees}",
	year          = 2004,
}