1. Aiba, A., K. Sakai, Y. Sato, D.J. Hawley and R. Hasegawa (1988). Constraint Logic Programming CAL. In.: Proc. of the International Conference on Fifth Generation Computer Systems, pp. 263–276. ICOT, Tokyo.
2. Maintaining Knowledge about Temporal Intervals;Allen;Communications of the ACM,1983
3. Trilogy (users manual);Andrews,1987
4. ECLiPSe 3.4 (Extensions User Manual);Brisset,1994
5. An Introduction to Prolog III;Colmeraurer;Com. ACM,1990