Ran-Zan Wang and  Yao-Ting Lee,  Visual Cryptography by Random Grids with Identifiable Shares.   journal   = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    May 2010, vol. 41(5). 965 - 970
    [viewed 26 January 2020]. Available from: https://publications.waset.org/pdf/1493.