Pitocchelli, Jay; John F. Piatt; Harry R. Carter (2003). ”Variation in plumage, molt, and morphology of the Whiskered Auklet (Aethia pygmaea) in Alaska”. Journal of Field Ornithology 74 (1): sid. 90–98. doi:10.1648/0273-8570(2003)74[90:VIPMAM]2.0.CO;2.
Chernova, O. F.; Fadeeva, E. O. (2009). ”The peculiar architectonics of contour feathers of the emu (Dromaius novaehollandiae, Struthioniformes)”. Doklady Biological Sciences 425: sid. 175–179. doi:10.1134/S0012496609020264.
Hieronymus, Tobin L.; Witmer, Lawrence M. (2010). ”Homology and Evolution of Avian Compound Rhamphothecae”. The Auk 127 (3): sid. 590–604. doi:10.1525/auk.2010.09122.
Klasing, Kirk C. (1999). ”Avian gastrointestinal anatomy and physiology”. Seminars in Avian and Exotic Pet Medicine 8 (2): sid. 42–50. doi:10.1016/S1055-937X(99)80036-X.