Nithima Hanmeng, and Poramate Pranayanuntana. “A Sinusoidal Nonlinear Oscillator with Adjustable Frequency”. Agriculture and Natural Resources 43, no. 5 (December 31, 2009): 372–378. accessed September 12, 2026. https://li01.tci-thaijo.org/index.php/anres/article/view/244845.