Dinh, Nguyen Van. “A Modified Asymptotic Method for a Van-Der-Pol Oscillator With Large Cubic Restoring Nonlinearity”. <i>Vietnam Journal of Mechanics</i> 26, no. 2 (June 1, 2004): 122–128. Accessed January 10, 2026. https://vjmech.vast.vn/vjmech/article/view/5696.