Pere Pardo; Pilar Dellunde; Lluís Godo "Secure and Optimal Base Contraction in Graded {\L}ukasiewicz Logics", Artificial Intelligence Research and Development. Proceedings of the 12th International Conference of the Catalan Association fo Artificial Intelligence. Frontiers in Aritficial Intelligence and Applications, vol. 202, Cardona, Catalonia, Spain, IOS Press, pp. 265-274, 21/10/2009. Abstract