1. Retinas of the electric ray, Narcine brasiliensis and the freshwater stingray;Anctil;Paratrygon motoro,1973
2. Techniques Histologiques;Gabe,1968
3. Cones in the retina of lemon shark (Negaprion hrevirostris);Gruber;Vision Res.,1963
4. L'oeil et la vision;Rochon-Duvigneaud,1958
5. Cited in Stell and Witkovsky;Shibkova,1972