KEZLAN, T. P. ON A THEOREM OF YEN. Tamkang Journal of Mathematics, [S. l.], v. 28, n. 1, p. 47–50, 2021. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4333. Acesso em: 5 may. 2024.