Stepanets , A.I. (1988) “Approximation by the Fourier operators of the functions preset on a real axis”, Ukrains’kyi Matematychnyi Zhurnal, 40(2), pp. 198–209. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/9116 (Accessed: 6 December 2025).