Mohammad Taghi Darvishi and  Samad Kheybari,  Application of He’s Parameter-Expansion Method to a Coupled Van Der Pol oscillators with Two Kinds of Time-delay Coupling.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    February 2011, vol. 50(2). 145 - 150
    [viewed 19 April 2024]. Available from: https://publications.waset.org/pdf/7039.