Hieu, D. V., et al. “Analysis of Nonlinear Oscillator Arising in the Microelectromechanical System by Using the Parameter Expansion and Equivalent Linearization Methods”. International Journal of Engineering & Technology, vol. 7, no. 2, Apr. 2018, pp. 597-04, https://doi.org/10.14419/ijet.v7i2.9191.