1. Studien uber die accommodation des vogelauges;Beer;Archiev Gesamte Physiolgie,1893
2. Het accommodatievermogen der oogen, physiologisch toegelicht;Cramer,1853
3. The description of an organ by which the eyes of birds are accommodated to the different distances of objects;Crampton;Thompson's Annals of Philosophy,1813
4. Differential accommodation in the lower visual field of the pigeon eye;Erichsen;Society for Neuroscience Abstracts,1993
5. In vitro changes in focal length of chick and pigeon lenses: Species differences and the effects of aging;Glasser;Investigative Ophthalmology and Visual Science,1994