Mas, M.; Monserrat, M.; Torrens, J., "Modus Ponens and Modus Tollens in discrete implications ", "International Journal of Approximate Reasoning", Volume 49, Pages 422-435, 2008. Paper.
Trillas, E.; Mas, M.; Monserrat, M.; Torrens, J., "On the representation of fuzzy rules", "International Journal of Approximate Reasoning", Volume 48, Pages 583-597, 2008. Paper.