@article{PORMA_1992__49_2_115790,
     author = {Figallo, Aldo V.},
     title = {On the congruences in four-valued modal algebras},
     journal = {Portugaliae mathematica},
     pages = {249--261},
     publisher = {mathdoc},
     volume = {49},
     number = {2},
     year = {1992},
     mrnumber = {1201977},
     zbl = {0787.03060},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1992__49_2_115790/}
}