BabenkoV. F.; KorneichukN. P.; KofanovV. A.; PichugovS. A. Inequalities for upper bounds of functionals on the classes $W^r H^{ω}$ and their applications. Ukrains’kyi Matematychnyi Zhurnal, v. 52, n. 1, p. 66-84, 25 Jan. 2000.