@inproceedings{PLEASE-2011-Livengood,
	author        = "Steve Livengood",
	booktitle     = "{Proceedings of the Second International Workshop on Product LinE Approaches in Software Engineering}",
	doi           = "10.1145/1985484.1985487",
	isbn          = "978-1-4503-0584-6",
	pages         = "6--9",
	publisher     = "{ACM}",
	title         = "{Issues in software product line evolution: complex changes in variability models}",
	year          = 2011,
}