HOSEN, M. A. Determination of Approximate Periods of Duffing-harmonic Oscillator. Walailak Journal of Science and Technology (WJST), [S. l.], v. 12, n. 10, p. 923–931, 2014. Disponível em: https://wjst.wu.ac.th/index.php/wjst/article/view/962. Acesso em: 29 apr. 2024.