1. K. R. Apt. Introduction to Logic Programming. In J. van Leeuvven, editor, Handbook of Theoretical Computer Science, volume B: Formal Models and Semantics. Elsevier, Amsterdam and The MIT Press, Cambridge, 1990.
2. C. Aravidan and P. M. Dung. On the correctness of Unfold/Fold transformation of normal and extended logic programs. Technical report, Division of Computer Science, Asian Institute of Technology, Bangkok, Thailand, April 1993.
3. M. Baudinet. Logic Programming Semantics: Techniques and Applications. PhD thesis, Stanford University, Stanford, California, 1989.
4. A. Bossi and N. Cocco. Basic Transformation Operations which preserve Computed Answer Substitutions of Logic Programs. Journal of Logic Programming, 16:47–87, 1993.
5. A. Bossi and N. Cocco. Preserving universal termination through unfold/fold. Technical Report 16, Dip. Matematica Pura e Applicata, Università di Padova, Italy, June 1994.