@inproceedings{STOC-1983-Engelfriet,
	author        = "Joost Engelfriet",
	booktitle     = "{Proceedings of the 15th Annual ACM Symposium on Theory of Computing}",
	doi           = "10.1145/800061.808767",
	pages         = "365--373",
	publisher     = "{ACM}",
	title         = "{Iterated Pushdown Automata and Complexity Classes}",
	year          = 1983,
}