Levy-Lior A, Pokroy B, Levavi-Sivan B, Leiserowitz L, Weiner S, Addadi L (2008). „Biogenic guanine crystals from the skin of fish may be designed to enhance light reflectance”. Crystal Growth & Design. 8 (2). стр. 507—511. doi:10.1021/cg0704753.
Sawyer RH, Knapp LW (август 2003). „Avian skin development and the evolutionary origin of feathers”. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. 298 (1): 57—72. PMID12949769. doi:10.1002/jez.b.26.CS1 одржавање: Формат датума (веза)
Sawyer RH, Knapp LW (август 2003). „Avian skin development and the evolutionary origin of feathers”. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. 298 (1): 57—72. PMID12949769. doi:10.1002/jez.b.26.CS1 одржавање: Формат датума (веза)