Geodesic
Best Polynomial Approximations and the Widths of Function Classes in~$L_{2}$
Matematičeskie zametki, Tome 94 (2013) no. 6, pp. 908-917.

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Sharp Jackson–Stechkin type inequalities in which the modulus of continuity of $m$th order of functions is defined via the Steklov function are obtained. For the classes of functions defined by these moduli of continuity, exact values of various $n$-widths are derived.
Keywords: best polynomial approximation, Jackson–Stechkin type inequality, function classes in $L_{2}$. 
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M. Sh. Shabozov; K. Tukhliev. Best Polynomial Approximations and the Widths of Function Classes in~$L_{2}$. Matematičeskie zametki, Tome 94 (2013) no. 6, pp. 908-917. http://geodesic.mathdoc.fr/item/MZM_2013_94_6_a9/

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