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2. N. I. Akhiezer, Lectures on the Theory of Approximation [in Russian], Nauka, Moscow (1965).
3. I. I. Ibragimov, Theory of Approximation by Entire Functions [in Russian], Elm, Baku (1979).
4. A. I. Stepanets, ?Approximation by Fourier Operators of functions defined on the real line,? Ukr. Mat. Zh.,40, No. 2, 198?209 (1988).
5. A. I. Stepanets, ?Approximation by entire functions in the uniform metric,? in: Approximation by Entire Functions on the Real Line [in Russian], Kiev (1988), pp. 3?47 (Preprint, Inst. Mat. Akad. Nauk UkrSSR; 88.27).