HE, Ji-Huan. Periodic Solutions for a Kind of Nonlinear Oscillations by a New Asymptotic Approach. Engineering Transactions, [S. l.], v. 50, n. 1-2, p. 35–42, 2015. DOI: 10.24423/engtrans.506.2002. Disponível em: https://et.ippt.pan.pl/index.php/et/article/view/506. Acesso em: 23 jul. 2025.