“Exact and Approximate Values of the Period for a ‘Truly Nonlinear’ Oscillator: $\ddot{x} + x + x^{1/3} = 0$”, Adv. Appl. Math. Mech., vol. 1, no. 3, pp. 383–390, Aug. 2018, Accessed: Mar. 14, 2026. [Online]. Available: https://gsp.tricubic.dev/aamm/article/view/4474