@inproceedings{CSL-2010-MartinM,
	author        = "Barnaby Martin and Jos Martin",
	booktitle     = "{Proceedings of the 19th EACSL Annual Conference / 24th International Workshop on Computer Science Logic}",
	doi           = "10.1007/978-3-642-15205-4_33",
	isbn          = "978-3-642-15204-7",
	pages         = "426--438",
	publisher     = "{Springer International Publishing}",
	series        = "{Lecture Notes in Computer Science}",
	title         = "{The Complexity of Positive First-Order Logic without Equality II: The Four-Element Case}",
	volume        = 6247,
	year          = 2010,
}