PACHPATTE, B. G. Inequalities applicable in the theory of partial finite difference equations. Tamkang Journal of Mathematics, [S. l.], v. 32, n. 2, p. 155–166, 2001. DOI: 10.5556/j.tkjm.32.2001.359. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/359. Acesso em: 28 mar. 2024.