1. A color notation;Munsell,1981
2. An analysis of tooth color;Clark;JADA,1931
3. Color matching in dentistry. The three-dimensional nature of color;Sproull;J Prosthet Dent,1973
4. Colour and fluorescence measurements on human teeth and dental porcelain;Clarke,1974
5. Tooth color selection;Clark;JADA,1933