Romanyuk, A.S. (2002) “Approximation of Classes $B_{p,θ}^r$ by Linear Methods and Best Approximations”, Ukrains’kyi Matematychnyi Zhurnal, 54(5), pp. 670–680. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4106 (Accessed: 10 April 2025).