@inproceedings{ICALP-1993-CzumajG,
	author        = "Artur Czumaj and Alan Gibbons",
	booktitle     = "{Proceedings of the 20th International Colloquium on Automata, Languages and Programming}",
	doi           = "10.1007/3-540-56939-1_64",
	isbn          = "3-540-56939-1",
	pages         = "88--101",
	publisher     = "{Springer-Verlag}",
	series        = "{Lecture Notes in Computer Science}",
	title         = "{Problems on Pairs of Trees and the Four Colour Problem of Planar Graphs}",
	volume        = 700,
	year          = 1993,
}