N. Rescher, Many-Valued Logic, 1969.
DOI : 10.1007/978-94-017-3546-9_6

S. Gottwald, A treatise on many-valued logics, ser. Studies in logic and computation, 2001.

D. Dubois, On Ignorance and Contradiction Considered as Truth-Values, Logic Journal of IGPL, vol.16, issue.2, pp.195-216, 2008.
DOI : 10.1093/jigpal/jzn003

A. Revault-d-'allonnes and M. Lesot, Formalising information scoring in a multivalued logic framework, Proc. of IPMU'14, pp.314-323, 2014.
URL : https://hal.archives-ouvertes.fr/hal-01215584

R. Yager, On some new classes of implication operators and their role in approximate reasoning, Information Sciences, vol.167, issue.1-4, pp.193-216, 2004.
DOI : 10.1016/j.ins.2003.04.001