1. Black, M.: Reasoning with Loose Concepts. Dialogue 2, 1–12 (1963)
2. Masquelet, A.C.: Le Raisonnement Médical. PUF, Paris (2006) (in French)
3. Sorensen, R.A.: Vagueness and Contradiction. Clarendon Press, Oxford (2001)
4. Trillas, E.: On Negation Functions in Fuzzy Set Theory. In: Barro, S., Bugarin, A., Sobrino, A. (eds.) Advances of Fuzzy Logic, pp. 31–43. Universidad de Santiago de Compostela (1998)
5. Trillas, E.: Conjectures in De Morgan Algebras and with Fuzzy Sets. Submitted to NAFIPS 2012 (2012)