PACHPATTE, B. G. On certain nonlinear integral inequalities involving iterated integrals. Tamkang Journal of Mathematics, [S. l.], v. 37, n. 3, p. 261–271, 2006. DOI: 10.5556/j.tkjm.37.2006.171. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/171. Acesso em: 19 aug. 2022.