@inproceedings{STOC-1970-LandweberR,
	author        = "Lawrence H. Landweber and Edward L. Robertson",
	booktitle     = "{Proceedings of the Second Annual ACM Symposium on Theory of Computing}",
	doi           = "10.1145/800161.805146",
	pages         = "31--36",
	publisher     = "{ACM}",
	title         = "{Recursive Properties of Abstract Complexity Classes}",
	year          = 1970,
}