Fedunyk-Yaremchuk O, Hembars'ka S. Best orthogonal trigonometric approximations of the Nikol’skii-Besov-type classes of periodic functions of one and several variables. Carpathian Math. Publ. [Internet]. 2022 Jun. 22 [cited 2024 Nov. 21];14(1):171-84. Available from: https://ktipe.pnu.edu.ua/index.php/cmp/article/view/5928