WASET
    Katsuhiro Narikiyo and  Shota Hashikawa,  A Way of Converting Color Images to Gray Scale Ones for the Color-Blind -Applying to the Part of the Tokyo Subway Map-.   journal   = {International Journal of Humanities and Social Sciences}, [online]. World Academy of Science, Engineering and Technology.
    January 2013, vol. 84(12). 1607 - 1611
    [viewed 29 March 2024]. Available from: https://publications.waset.org/pdf/9997024.