Rochdi Omami and  Mohamed Omami and  Raouf Ouni,  Group of Square Roots of Unity Modulo n.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    July 2009, vol. 31(7). 505 - 513
    [viewed 11 April 2021]. Available from: https://publications.waset.org/pdf/8554.