@inproceedings{GPCE-2012-WalkingshawE,
	author        = "Eric Walkingshaw and Martin Erwig",
	booktitle     = "{Proceedings of the 11th International Conference on Generative Programming and Component Engineering}",
	doi           = "10.1145/2371401.2371421",
	isbn          = "978-1-4503-1129-8",
	pages         = "132--140",
	publisher     = "{ACM}",
	title         = "{A calculus for modeling and implementing variation}",
	year          = 2012,
}