Serdyuk АS, Stepaniuk Т. Estimates of the best orthogonal trigonometric approximations of the classes of convolutions of periodic functions of not high smoothness . Dopov. Nac. akad. nauk Ukr. [Internet]. 2015 Jul. 28 [cited 2026 Jun. 20];(7):13-9. Available from: https://nasu-periodicals.org.ua/index.php/dp/article/view/15066