Font, Josep M.Rius Font, Miquel2020-03-032020-03-031989https://hdl.handle.net/2445/151824Preprint enviat per a la seva publicació en una revista científica. Proceedings of the Twentieth International Symposium on Multiple-Valued Logic, 1990, pp. 85-92. [http://doi.org/10.1109/ISMVL.1990.122601]We study the class of abstract logics projectively generated by the class of tetravalent modal algebras. They are modal logics and they turn out to be four-valued in the sense that they can be characterized using the natural logic on the four-element tetravalent modal algebra which generates this variety together with sorne special class of homomorphisms. We also characterize them by their abstract properties and prove a completeness theorem.19 p.application/pdfeng(c) Josep M. Rius et al., 1989Lògica matemàticaLògica algebraicaTeoria de la computacióUniversitat de Barcelona. Institut de Matemàticainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccess