Mutsuko Nichogi Takehisa Tanaka Osamu Yamada Katsuhiro Kanamori Color reproduction of teeth and gums image. 24-32 2001 32 Systems and Computers in Japan 3 http://dx.doi.org/10.1002/1520-684X(200103)32:3%3c24::AID-SCJ3%3e3.0.CO;2-Q db/journals/scjapan/scjapan32.html#NichogiTYK01