@inproceedings{CSL-1989-Gradel,
	author        = "Erich Grädel",
	booktitle     = "{Proceedings of the Third Workshop on Computer Science Logic}",
	doi           = "10.1007/3-540-52753-2_38",
	isbn          = "3-540-52753-2",
	pages         = "163--175",
	publisher     = "{Springer-Verlag}",
	series        = "{Lecture Notes in Computer Science}",
	title         = "{On Logical Descriptions of Some Concepts in Structural Complexity Theory}",
	volume        = 440,
	year          = 1989,
}