H. Taghvafard and  G. H. Erjaee,  Two-dimensional Differential Transform Method for Solving Linear and Non-linear Goursat Problem.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    March 2010, vol. 39(3). 432 - 435
    [viewed 21 January 2020]. Available from: https://publications.waset.org/pdf/6124.