Stepanets OI. Approximation of $\bar {\psi} - integrals$−integrals of periodic functions by Fourier sums (small smoothness). Iof periodic functions by Fourier sums (small smoothness). I. Ukr. Mat. Zhurn. [Internet]. 1998Feb.25 [cited 2024Nov.24];50(2):274-91. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/4961