1. Bauernfeind JC (1981) Carotenoids as colorants and vitamin A precursors: technological and nutritional applications. Academic, New York
2. Berthold P (1967) Über Haftfarben bei Vögeln: Rostfärbung durch Eisenoxid beim Bartgeier (Gypaetus barbatus) und bei anderen Arten. Zool Jahrb Syst 93:507?595
3. Blair JA, Graham J (1954) The pigments of snake skins. 1. The isolation of riboflavin as a pigment of the skins of the green snakes Philothamnus semivariegatus and Dispholidus typus. Biochem J 56:286?287
4. Britton G (1985) General carotenoid methods. Methods Enzymol 111:507?595
5. Britton G, Liaaen-Jensen S, Pfander H (1995) Carotenoids. Volume 1A: isolation and analysis. Birkhäuser, Basel