Guixia Lv and  Longjun Shen,  A Finite Point Method Based on Directional Derivatives for Diffusion Equation.   journal   = {International Journal of Physical and Mathematical Sciences}, [online]. World Academy of Science, Engineering and Technology.
    September 2011, vol. 57(9). 1449 - 1454
    [viewed 26 April 2024]. Available from: https://publications.waset.org/pdf/7710.