Martin, Graham R. (25 juni 1999). ”Visual fields in short-toed eagles, Circaetus gallicus (Accipitridae), and the
function of binocularity in birds”. Brain, Behaviour and Evolution "53" (2): ss. 55–66. doi:10.1159/000006582. PMID 9933782.
Williams, David L. (25 juni 2003). ”Symblepharon with aberrant protrusion of the nictitating membrane in the snowy owl
(Nyctea scandiaca)”. Veterinary Ophthalmology "6" (1): ss. 11–13. doi:10.1046/j.1463-5224.2003.00250.x. PMID 12641836.
Andersson, S. (25 juni 1998). ”Ultraviolet sexual dimorphism and assortative mating in blue tits”. Proceeding of the Royal Society B "265" (1395): ss. 445–50. doi:10.1098/rspb.1998.0315.
Viitala, Jussi (25 juni 1995). ”Attraction of kestrels to vole scent marks visible in ultraviolet light”. Nature "373" (6513): ss. 425–27. doi:10.1038/373425a0.
Hayes, Brian (25 juni 1991). ”Novel area serving binocular vision in the retinae of procellariiform seabirds”. Brain, Behavior and Evolution "37" (2): ss. 79–84. doi:10.1159/000114348.
Martin, Graham R. (25 juni 1991). ”The Eye of a Procellariiform Seabird, the Manx Shearwater, Puffinus puffinus: Visual Fields and Optical Structure”. Brain, Behaviour and Evolution "37" (2): ss. 65–78. doi:10.1159/000114347.
Martin, Graham R. (25 juni 1999). ”Visual fields in short-toed eagles, Circaetus gallicus (Accipitridae), and the
function of binocularity in birds”. Brain, Behaviour and Evolution "53" (2): ss. 55–66. doi:10.1159/000006582. PMID 9933782.
Williams, David L. (25 juni 2003). ”Symblepharon with aberrant protrusion of the nictitating membrane in the snowy owl
(Nyctea scandiaca)”. Veterinary Ophthalmology "6" (1): ss. 11–13. doi:10.1046/j.1463-5224.2003.00250.x. PMID 12641836.
Wilkie, Susan E. (25 juni 1998). ”The molecular basis for UV vision in birds: spectral characteristics, cDNA sequence and
retinal localization of the UV-sensitive visual pigment of the budgerigar (Melopsittacus
undulatus)”. Biochemical Journal "330": ss. 541–47. PMID 9461554.
Jochen Schuck, Holger Gerhardt, Hartwig Wolburg (2000) The peripapillary glia of the optic nerve head in the chicken retina, The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology, Vol.259, nr.3, sid:263-275, DOI 10.1002/1097-0185(20000701)259:3<263::AID-AR40>3.0.CO;2-W, html-sammanfattning
Cleere, Nigel; Nurney, David (1998). Nightjars: A Guide to the Nightjars, Frogmouths, Potoos, Oilbird and Owlet-nightjars of the World. Pica / Christopher Helm. sid. 7. ISBN 1873403488. OCLC39882046