Ou Xie and  Zhenyu Zhao,  Identifying an Unknown Source in the Poisson Equation by a Modified Tikhonov Regularization Method.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    August 2012, vol. 68(8). 1128 - 1132
    [viewed 18 October 2021]. Available from: https://publications.waset.org/pdf/892.