Pachpatte, B. G. “On Certain Nonlinear Integral Inequalities Involving Iterated Integrals”. Tamkang Journal of Mathematics 37, no. 3 (September 30, 2006): 261–271. Accessed April 25, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/171.