Solich, K.V. (2011) “Best bilinear approximations of the classes $S^{\Omega}_{p, \theta}B$ of periodic functions of many variables”, Ukrains’kyi Matematychnyi Zhurnal, 63(6), pp. 809–826. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/2764 (Accessed: 5 December 2025).