PACHPATTE, B. G. Inequalities similar to Opial’s inequality involving higher order derivatives. Tamkang Journal of Mathematics, [S. l.], v. 36, n. 2, p. 111-117, 2005. DOI: 10.5556/j.tkjm.36.2005.123. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/123. Acesso em: 23 may. 2022.