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For each k> k > 2, three logical-functional languages are introduced for the set of functions of k-valued logic: the positive expressibility language Pos*, the first-order language l L*, and the second-order language 2L*. On the basis of the notion of expressibility in a language, the corresponding closure operators are defined. It is proved that the operators of 1 L*-closure and 2L*-closure coincide. The 1 L^-closed and Pos^-closed classes are described with the help of symmetric groups and symmetric semigroups. The expressibility in the languages 1L* and Pos* is compared with the parametric expressibility and the expressibility by terms.

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