Ching-Sheng Hsu and  Young-Chang Hou,  A Visual Cryptography and Statistics Based Method for Ownership Identification of Digital Images .   journal   = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    February 2007, vol. 2(2). 461 - 464
    [viewed 28 February 2020]. Available from: https://publications.waset.org/pdf/9964.