@inproceedings{PPDP-2007-Charatonik,
	author        = "Witold Charatonik",
	booktitle     = "{Proceedings of the Ninth International Conference on Principles and Practice of Declarative Programming}",
	doi           = "10.1145/1273920.1273949",
	isbn          = "978-1-59593-769-8",
	pages         = "209",
	publisher     = "{ACM}",
	title         = "{Regular directional types for logic programs}",
	year          = 2007,
}