ZadereiP. V. “Approximation of $(\bar \psi ,\bar \beta )$ -Differentiable Periodic Functions of Many Variables”. Ukrains’kyi Matematychnyi Zhurnal 45, no. 3 (March 25, 1993): 367-377. Accessed October 6, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5818.