Some inequalities between the best polynomial approximations and averaged finite-difference norms in space \(L_2\). (English. Russian original) Zbl 1494.41006
Russ. Math. 65, No. 10, 69-81 (2021); translation from Izv. Vyssh. Uchebn. Zaved., Mat. 2021, No. 10, 78-91 (2021).