@article{GT-VMT-2006-Willink08,
	author        = "Edward D. Willink",
	doi           = "10.1016/j.entcs.2008.04.039",
	journal       = "{Electronic Notes in Theoretical Computer Science}",
	pages         = "171--179",
	title         = "{On Challenges for a Graphical Transformation Notation and the UMLX Approach}",
	volume        = 211,
	year          = 2008,
}