@inproceedings{STOC-1979-ValdesTL,
	author        = "Jacobo Valdes and Robert Endre Tarjan and Eugene L. Lawler",
	booktitle     = "{Proceedings of the 11th Annual ACM Symposium on Theory of Computing}",
	doi           = "10.1145/800135.804393",
	pages         = "1--12",
	publisher     = "{ACM}",
	title         = "{The recognition of Series Parallel digraphs}",
	year          = 1979,
}