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Translated from Matematicheskie Zametki, Vol. 48, No. 3, pp. 91–99, September, 1990.
The author is thankful to S. B. Stechkin and V. A. Baskakov for useful discussions.
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Magaril-Il'yaev, G.G. Exact solutions of some approximation problems by means of positive operators. Mathematical Notes of the Academy of Sciences of the USSR 48, 938–944 (1990). https://doi.org/10.1007/BF01157438
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DOI: https://doi.org/10.1007/BF01157438