NAIMI, M.; BENHARRAT, M. On the numerical radius of an upper triangular operator matrix. Tamkang Journal of Mathematics, [S. l.], v. 55, n. 2, p. 195–201, 2023. DOI: 10.5556/j.tkjm.55.2024.5094. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/5094. Acesso em: 18 may. 2024.