BITIMKHAN, S.; MEKESH, O. Best approximation by «angle» and the absolute Cesàro summability of double Fourier series. Bulletin of the Karaganda University. Mathematics Series, [S. l.], v. 112, n. 4, p. 56–65, 2023. DOI: 10.31489/2023m4/56-65. Disponível em: https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/605. Acesso em: 2 jul. 2025.