Jiming Yang,  Alternative Convergence Analysis for a Kind of Singularly Perturbed Boundary Value Problems.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    April 2011, vol. 52(4). 670 - 673
    [viewed 17 February 2020]. Available from: https://publications.waset.org/pdf/8774.