@article{Shvai2016JCompAnalMath,
  author  = {Pozharska, K. and (Shvai K.)},
  title   = {The best {$M$}-term trigonometric approximations of classes of
             {$\psi,\beta$}-differentiable periodic multivariate
             functions in the space {$L_q$}},
  journal = {J. Comp. Appl. Math. of the Taras Shevchenko National
             University of Kyiv},
  volume  = {122},
  number  = {2},
  pages   = {83--91},
  year    = 2016,
 url = {http://jnam.lnu.edu.ua/pdf/y2016_no2(122)_art07_shvai.pdf},
  }