Pure three-valued Łukasiewiczian implication
Storrs McCall, R. Meyer · Journal of Symbolic Logic · 1966
The matrix defining Łukasiewicz's three-valued logic, constructed in 1920 and described at length in [1], is the following: This matrix was axiomatized in 1931 by Wajsberg (see [6]), who showed that the following axioms together with the rules of substitution and modus ponens were sufficient: