Two Variations on the Theme of "Useful Four-Valued Logic".

In what follows two curious generalizations of four-element matrixes for first-degree relevant logic will be presented. The first part of the paper deals with the semantic consideration and algebraic analysis of inconsistent logic PR (P for paraconsistent, and R for relevant), to be result of combining matrixes for the system FDE with the matrix for classical implication. In the second part the variant of propositional logic with certain "non-monotonic" properties is considered. [ABSTRACT FROM AUTHOR]