@inproceedings{STOC-1970-Cook,
	author        = "Stephen A. Cook",
	booktitle     = "{Proceedings of the Second Annual ACM Symposium on Theory of Computing}",
	doi           = "10.1145/800161.805151",
	pages         = "70--72",
	publisher     = "{ACM}",
	title         = "{Path Systems and Language Recognition}",
	year          = 1970,
}