@inproceedings{CSL-1991-Seibert,
	author        = "Sebastian Seibert",
	booktitle     = "{Proceedings of the Fifth Workshop on Computer Science Logic}",
	doi           = "10.1007/BFb0023779",
	isbn          = "3-540-55789-X",
	pages         = "329--352",
	publisher     = "{Springer-Verlag}",
	series        = "{Lecture Notes in Computer Science}",
	title         = "{Quantifier Hierarchies over Word Relations}",
	volume        = 626,
	year          = 1991,
}