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2. V. N. Belykh, Sib. Math. J. 46 (3), 373–385 (2005).
3. H. Weyl, in Selected Works (Nauka, Moscow, 1984), pp. 58–93 [in Russian].
4. I. K. Daugavet, Introduction to Classical Function Approximation Theory (St. Petersburg, 2011) [in Russian].
5. V. M. Tikhomirov, Certain Issues of Approximation Theory (Mosk. Gos. Univ., Moscow, 1976) [in Russian].