1. Dodge, R., Amer. J. Physiol., 8, 307 (1903).
2. Westheimer, G., A.M.A. Archives of Ophthalmology, 52 (1954).
3. Helmholtz, H. von, “Physiological Optics”, trans. J. P. C. Southall (Amer. Optical Soc., 1924).
4. Mackay, D. M., Nature, 181, 507 (1958).
5. Kornmüller, A. E., J. f. Psychol. und Neurol., 41, 354 (1930).