1. von Helmholtz, H. Treatise on Physiological Optics vol. 3 (1910) (trans. Southall, J. P. C.) (Dover, New York, 1963).
2. von Holst, E. & Mittelstaedt, H. Das Reafferenzprinzip. Naturwissenschaften 37, 464–476 (1950).
3. MacKay, D. M. in Handbook of Sensory Physiology vol. VII/3: Central Processing of Visual Information (ed. Jung, R.) 307–331 (Springer, Berlin, 1973).
4. Matin, L. in Handbook of Sensory Physiologyvol. VII/4: Visual Psychophysics (eds Jameson, D. & Hurvich, L. M.) 331–380 (Springer, Berlin, 1972).
5. Skavenski, A. A., Haddad, G. M. & Steinman, R. M. The extraretinal signal for the visual perception of direction. Percept. Psychophys. 11, 287–290 (1972).