1. Spectral Transmission and Reflection Measurements;McNicholas;Bur. Standards J. Res,1928
2. Psychology of Color in Relation to Illumination;Troland;Tr. Illum. Eng. Soc,1918
3. Introduction to Study of Color Vision;Parsons,1915
4. Report of Committee on Colorimetry;Troland;J. Optical Soc. America,1922
5. By the selection of the latter method, it is not to be inferred that spectral measurements are of no value in dentistry. On the contrary, they are of exceptional value for certain requirements, such as, for example, the development of a non silicate ceramic cement that will not influence and change the apparent color of the tooth under varying illuminating conditions. It is quite possible to make one material match another material in spectral character, since both materials derive their color from pigments. It is difficult to estimate the chemical and physical possibilities of developing dental restorative materials that will exactly match natural tooth structure in its spectral distribution.