Yanling Zhu and  Kai Wang,  Periodic Solutions for a Third-order p-Laplacian Functional Differential Equation.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    July 2010, vol. 43(7). 808 - 811
    [viewed 23 January 2020]. Available from: https://publications.waset.org/pdf/9542.