1. Yarbus, A. L., Eye Movements and Vision (Plenum, New York, 1967).
2. Mittelstaedt, H., Symp. Soc. Exp. Biol., 18, 365 (1964).
3. Wilson, D. M., and Hoy, R. R., Z. Vergl. Physiol., 58, 136 (1968).
4. Reichardt, W. E., The Neurosciences: Second Study Program (edit. by Schmitt, F. O.), 494 (Rockefeller, New York, 1970).
5. Land, M. F., J. Exp. Biol., 54, 119 (1971).