Troland, L. T. (August 1922). "Report of Committee on Colorimetry for 1920–21". Journal of the Optical Society of America. 6 (6): 527–96. doi:10.1364/JOSA.6.000527. The report defined colour as follows: "Colour is the general name for all sensations arising from the activity of the retina of the eye and its attached nervous mechanisms, this activity being, in nearly every case in the normal individual, a specific response to radiant energy of certain wave-lengths and intensities."