@inproceedings{ICALP-1980-EhrenfeuchtR,
	author        = "Andrzej Ehrenfeucht and Grzegorz Rozenberg",
	booktitle     = "{Proceedings of the Seventh Colloquium on Automata, Languages and Programming}",
	doi           = "10.1007/3-540-10003-2_66",
	isbn          = "3-540-10003-2",
	pages         = "134--141",
	publisher     = "{Springer-Verlag}",
	series        = "{Lecture Notes in Computer Science}",
	title         = "{DOS Systems and Languages}",
	volume        = 85,
	year          = 1980,
}