1. Benson, B., Freuder, E.: Interchangeability preprocessing can improve forward checking search. In: Proc. of the 10th ECAI, Vienna, Austria. (1992) 28–30
2. Bistarelli, S.: Soft Constraint Solving and programming: a general framework. PhD thesis, Dipartimento di Informatica, Università di Pisa, Italy (2001)
3. Bistarelli, S., Fargier, H., Montanari, U., Rossi, F., Schiex, T., Verfaillie, G.: Semiring-based CSPs and Valued CSPs: Frameworks, properties, and comparison. CONSTRAINTS: An international journal. Kluwer 4 (1999)
4. Bistarelli, S., Montanari, U., Rossi, F.: Constraint Solving over Semirings. In: Proc. IJCAI95, San Francisco, CA, USA, Morgan Kaufman (1995)
5. Bistarelli, S., Montanari, U., Rossi, F.: Semiring-based Constraint Solving and Optimization. Journal of the ACM 44 (1997) 201–236