1. A. S. Romanyuk, "Entropy numbers and widths for the classes $$ {B}_{p,\theta}^r $$ of periodic functions of many variables," Ukr. Mat. Zh., 68, No. 10, 1403-1417 (2016)
2. English translation: Ukr. Math. J., 68, No. 10, 1620-1636 (2017).
3. M. V. Hembars’kyi and S. B. Hembars’ka, “Widths of the classes $$ {B}_{p,\theta}^{\Omega} $$ of periodic functions of many variables in the space B1,1,” Ukr. Mat. Visn., 15, No. 1, 43–57 (2018).
4. D. Dung, V. N. Temlyakov, and T. Ullrich, Hyperbolic Cross Approximation, Birkhäuser, CRM Barcelona (2019).
5. A. S. Romanyuk, Approximating Characteristics of the Classes of Periodic Functions of Many Variables [in Russian], Proc. of the Institute of Mathematics, National Academy of Sciences of Ukraine, 93, Kyiv (2012).