VAKARCHUK, S. B.; SHABOZOV, M. Sh. Quasiwidths and optimization of methods of mixed approximation of multidimensional singular integrals with kernels of hilbert type. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 6, p. 753–770, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5276. Acesso em: 5 dec. 2025.