KonsevichN. M. Estimates of the Best $M$-Term Trigonometric Approximations of the Classes $L_{β, p}^{ψ}$ of Periodic Functions of Many Variables in the Space $L_q$. Ukrains’kyi Matematychnyi Zhurnal, v. 52, n. 7, p. 898-907, 25 Jul. 2000.