1. Abengózar-Carneros, M., Arenas-Sánchez, P., Caballero-Roldán, R., Gil-Luezas, A., González-Moreno, J.C., Leach-Albert, J., López-Fraguas, F.J., Martí-Oliet, N., Molina-Bravo, J.M., Pimentel-Sánchez, E., Rodríguez-Artalejo, M., Roldán-García, M.M., Ruz-Ortiz, J.J., Sánchez-Hernández, J.: TOY: A Multiparadigm Declarative Language. Version 2.0. Technical Report, Dpto. Sistemas Informáticos y Programación, Universidad Complutense de Madrid, February (2002). System and documentation available at http://toy.sourceforge.net.
2. Antoy, S., Echahed, R., Hanus, M.: A needed narrowing strategy. In: Proc. ACM Symp. on Principles of Programming Languages (POPL’94), pp. 268–279. ACM Press, Portland (1994)
3. Antoy, S., Echahed, R., Hanus, M.: A needed narrowing strategy. J. ACM 74(4), 776–822 (2000)
4. Aït-Kaci, H., Podelski, A.: A feature constraint system for logic programming with entailment. Theor. Comput. Sci. 122, 263–283 (1994)
5. Apt, K.R.: Logic programming. In: van Leeuwen, J. (ed.) Handbook of Theoretical Computer Science, vol. B, Chapter 10, pp. 493–574. Elsevier and The MIT Press (1990)