@INPROCEEDINGS {
	AUTHOR = "Pablo Barcel{\'o} and Miguel Romero and Thomas Zeume",
	TITLE = "A More General Theory of Static Approximations for Conjunctive Queries",
	BOOKTITLE = "21th International Conference on Database Theory (ICDT)",
	PAGES = "article 7",
	YEAR = "2018",
	PUBLISHER = "ACM Press",
	SERIES ="ACM International Conference Proceeding Series",
	}