Approximation by Nörlund Means of Hexagonal Fourier Series. Analysis in Theory and Applications, [S. l.], v. 33, n. 4, p. 384–400, 2017. DOI: 10.4208/ata.2017.v33.n4.8. Disponível em: https://global-sci.com/index.php/ata/article/view/8134. Acesso em: 6 dec. 2025.