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2. N.A. Lebedev and V.I. Smirnov, The constructive theory of functions of a complex variable. (Russian)Nauka, Moscow, 1964.
3. I.R. Lomidze, Criteria of unitary and orthogonal equivalence of operators.Bull. Acad. Sci. Georgia 141 (1991), No. 3, 481–483.
4. F.R. Gantmakher, The theory of matrices (Russian)Nauka, Moscow, 1988.