The Lattice of Extensions of the Modal Logic of Two Equivalence Relations Has the Cardinality of the Continuum  / Izmailov M.M. // Vestnik Moskovskogo Universiteta. Seriya 1. Matematika. Mekhanika. 2011. ? 4. P. 46-48 [Moscow Univ. Math. Bulletin. Vol. 66, N 4, 2011.].

A continuum of different logics over S5×S5 is constructed. This proves that the cardinality of the lattice of all normal extensions of the logic of two equivalence relations Ext(S5×S5) is continuum.

Key words: modal logic, fusion of logics, extensions of logics, logic of equivalence relation.