@article {DBLP:journals/jlp/BarbutiMPT90,
	title = {A Transformational Approach to Negation in Logic Programming},
	journal = {J. Log. Program.},
	volume = {8},
	number = {3},
	year = {1990},
	pages = {201-228},
	author = {Roberto Barbuti and Paolo Mancarella and Dino Pedreschi and Franco Turini}
}
@conference {DBLP:conf/tapsoft/BarbutiMPT87,
	title = {Intensional Negation of Logic Programs: Examples and Implementation Techniques},
	booktitle = {TAPSOFT, Vol.2},
	year = {1987},
	pages = {96-110},
	author = {Roberto Barbuti and Paolo Mancarella and Dino Pedreschi and Franco Turini}
}
