Li Xiguang,  The Symmetric Solutions for Boundary Value Problems of Second-Order Singular Differential Equation.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    August 2013, vol. 73(1). 156 - 160
    [viewed 19 April 2024]. Available from: https://publications.waset.org/pdf/16821.