Dinh, Nguyen Van, and Tran Duong Tri. “Frequency of a Vanderpol Oscillator With Large Cubic Restoring Nonlinearity”. Vietnam Journal of Mechanics 25, no. 4 (December 31, 2003): 195–200. Accessed January 2, 2026. https://vjs.ac.vn/vjmech/article/view/6591.