Meng Hu and  Lili Wang,  Periodic Solutions for Some Strongly Nonlinear Oscillators by He's Energy Balance Method.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    August 2012, vol. 68(8). 1133 - 1135
    [viewed 17 April 2024]. Available from: https://publications.waset.org/pdf/13750.