CHOU, C. N.; YANG, G.-S. A variant of the inequality given by Bainov and Simeonov. Tamkang Journal of Mathematics, [S. l.], v. 36, n. 4, p. 359-363, 2005. DOI: 10.5556/j.tkjm.36.2005.108. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/108. Acesso em: 24 may. 2022.