BASU, C. K. On $ \delta $-perfect functions. Tamkang Journal of Mathematics, [S. l.], v. 35, n. 3, p. 207–212, 2004. DOI: 10.5556/j.tkjm.35.2004.200. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/200. Acesso em: 26 apr. 2024.