1. Aubert, H., Moleschotts Untersuchungen zur Naturl., B2V, 279 (1858).
2. Baird, J. W., The Color Sensitivity of the Peripheral Retina (Wash., Carnegie Inst., 1905).
3. Helmholtz, H. von, Physiological Optics, 1924 ed., 2, 42 and elsewhere (1866).
4. Troxler, D., Himly, and Schmidt, Opthalmologische Bibliothek, 2, 2 (1804).
5. Aubert, H., and Förster, O., Allg. med. Zentralzeitung, Berlin, No. 33, 259 (as summarized in a sentence by Helmholtz) (1957).