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@article{AL_1992_31_2_a3, author = {L. L. Maksimova}, title = {Modal logics and varieties of modal algebras: the {Beth,}}, journal = {Algebra i logika}, pages = {145--166}, publisher = {mathdoc}, volume = {31}, number = {2}, year = {1992}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/AL_1992_31_2_a3/} }
L. L. Maksimova. Modal logics and varieties of modal algebras: the Beth,. Algebra i logika, Tome 31 (1992) no. 2, pp. 145-166. http://geodesic.mathdoc.fr/item/AL_1992_31_2_a3/