Оn the congruence lattices of periodic unary algebras

The author describes all commutative unary algebras with finite number of unary operations which have distributive lattice of congruences and cyclic elements in every operation. It proves the following result: Теорема 2. Let A = ???, ??1, ??2,..., ????? is a connected commutative unary algebra, ?? ? 1 and ??1, ??2,..., ???? ? 1 - such a natural numbers, that ?????? ?? (??) = ?? for every ?? ? ?? and every ?? ? ??. Then the following condition are equivalent: (1) The lattice of congruence on A has a distributive property. (2) One can find natural numbers ??1, ??2,..., ???? ? 1 and such an unary operation ? on A, that for every ?? = 1, 2,...,?? and every ?? ? ?? it holds ????(??) = ?????(??).