1. Apt, K., & Wallace, M. (2007). Constraint logic programming using ECLiPSe. Cambridge: Cambridge University Press.
2. Bowen, J. P. (1996). Formal specification and documentation using Z: A case study approach. Boston: International Thomson Computer Press.
3. Brand, S., Naroditskaya, N., Quimper, C.-G., Stuckey, P. J., & Walsh, T. (2007). Encodings of the sequence constaint. In Proceedings of the 13th international conference on principles and practice of constraint programming (CP2007), Providence, Rhode Island, USA (September).
4. Demoen, B., García de la Banda, M., Harvey, W., Marriott, K., & Stuckey, P. J. (1999). An overview of HAL. In Jaffar, J. (ed.), Proceedings of the fourth international conference on principles and practices of constraint programming, LNCS, (pp. 174–188). New York: Springer.
5. DIMACS, (1993). Satisfiability suggested format. ftp://dimacs.rutgers.edu/pub/challenge/satisfiability/doc .