1.
Shvai KV. Estimates of the best bilinear approximations for the classes of $(ψ,β)$-differentiable periodic multivariate functions. Ukr. Mat. Zhurn. [Internet]. 2018Apr.25 [cited 2024Dec.22];70(4):564-73. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/1576