VAKARCHUK, S.; VAKARCHUK, M. Approximation in the mean of the classes of functions in the space $L_2[(0,1);x]$ by the Fourier–Bessel sums and estimates of the values of their $n$-widths. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 76, n. 2, p. 198–223, 2024. DOI: 10.3842/umzh.v76i2.7763. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/7763. Acesso em: 5 dec. 2025.