@inproceedings{CSL-1990-Ranaivoson,
	author        = "Solomampionona Ranaivoson",
	booktitle     = "{Proceedings of the Fourth Workshop on Computer Science Logic}",
	doi           = "10.1007/3-540-54487-9_68",
	isbn          = "3-540-54487-9",
	pages         = "318--339",
	publisher     = "{Springer-Verlag}",
	series        = "{Lecture Notes in Computer Science}",
	title         = "{Nontrivial Lower Bounds for some NP-Problems on Directed Graphs}",
	volume        = 533,
	year          = 1990,
}