Said Laachir and  Aziz Laaribi,  Exact Solutions of the Helmholtz equation via the Nikiforov-Uvarov Method.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    November 2013, vol. 73(1). 170 - 173
    [viewed 26 April 2024]. Available from: https://publications.waset.org/pdf/9996665.