Color universal design: the selection of four easily distinguishable colors for all color vision types. - Yasuyo G. Ichihara; Masataka Okabe; Koichi Iga; Yosuke Tanaka; Kohei Musha; Kei Ito (Color Imaging: Processing, Hardcopy, and Applications, 2008)

Color universal design, the optimal representation of the color red for protan-vision people: practical alternatives from the color universal design organization. - Yasuyo G. Ichihara; Masataka Okabe; Koichi Iga; Yosuke Tanaka; Kohei Musha; Kei Ito (Color Imaging: Displaying, Processing, Hardcopy, and Applications, 2009)