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P9406   J.A. Bergstra, I. Bethke & P.H. Rodenburg
        "A propositional logic with 4 values: true, false, divergent and
        meaningless"


In this paper, we survey 3-valued logics and 
their complete axiomatizations, one of which is new.
We then propose a 4-valued, functionally complete logic that 
incorporates these 3-valued systems and provide notations for interesting 
operators and subsystems.