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3. G.H. Hardy and J.E. Littlewood, “Theorems concerning mean values of analytic or harmonic functions”, Quart. J. Math. (Oxford), 12, 221–256, 1941.
4. A. Zygmund, Trigonometric Series, vol. 2 (Cambridge Univ. Press, Cambridge, 1959).
5. M.M. Djrbashian, Integral Transforms and Representations of Functions in the Complex Domain [in Russian] (Nauka, Moscow, 1966).