TUNÇ, Cemil; ERDUR, Sultan. On the Existence of Periodic Solutions to Certain Non-linear Differential Equations of Third Order: On the Existence of Periodic Solutions. Proceedings of the Pakistan Academy of Sciences: A. Physical and Computational Sciences, [S. l.], v. 54, n. 2, p. 207–218, 2021. Disponível em: http://ppaspk.org/index.php/PPAS-A/article/view/251. Acesso em: 4 dec. 2025.