[1]
VakarchukS.B. 2016. Jackson-type inequalities with generalized modulus of continuity and exact values of the $n$-widths of the classes of $(ψ,β)$-differentiable functions in $L_2$. II. Ukrains’kyi Matematychnyi Zhurnal. 68, 8 (Aug. 2016), 1021-1036.