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Mas, M.; Mayor, G.; Torrens, J., "t-Operators and Uninorms on a Finite Totally Ordered Set", "International Journal of Intelligent Systems", Volume 14, Issue 9, Pages 909-922, 1999. Paper.
Mas, M.; Mayor, G.; Torrens, J., "t-Operators", "International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems", Volume 7, Issue 1, Pages 31-50, 1999. Paper.
Más M., Torrens J., Calvo, T. and Carbonell M., "Idempotent operators on a finite chain", "Mathware and Soft Computing", Volume 6, Issue 2-3, Pages 235-247, 1999. Paper.