1. BMDP statistical software;Dixon,1983
2. How birds look at objects;Erichsen,1979
3. Lower-field myopia in birds: An adaptation that keeps the ground in focus;Erichsen;Investigative Ophthalmology and Visual Science (Suppl.),1989
4. Refractive sectors in the visual field of the pigeon eye;Fitzke;Journal of Physiology,1985
5. Retinoscopy and eye size;Glickstein;Science, New York,1970