@inproceedings{LOPSTR-1999-LammelRL,
	author        = "Ralf Lämmel and Günter Riedewald and Wolfgang Lohmann",
	booktitle     = "{Selected Papers of the Ninth International Workshop on Logic Programming Synthesis and Transformation}",
	doi           = "10.1007/10720327_9",
	isbn          = "3-540-67628-7",
	pages         = "136--155",
	publisher     = "{Springer-Verlag}",
	series        = "{Lecture Notes in Computer Science}",
	title         = "{Roles of Program Extension}",
	volume        = 1817,
	year          = 1999,
}