Theorems on direct and inverse approximation by algebraic polynomials and piecewise polynomials in the spaces \(H^m(a,b)\) and \(B_{2,q}^s(a,b)\)
From the introduction: This paper is an extended presentation of the results announced earlier in a short communication [the author, Russ. Math. 66, No. 6, 65--72 (2022; Zbl 1528.41012)].
scientific article; zbMATH DE number 7868685
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