1. Pigmenters and poultry feeding;ADAMS,1985
2. ANON (1974). Egg yolk pigmentation with carophyll, (2nd Edition). F. Hoffmann-La Roche and Co. Ltd, Basle, Switzerland
3. ANON (1985). Animal Nutrition News, 30, (January), 1
4. Research on Egg Yolk Pigmentation and its Practical Application
5. FEEDING STUFFS (NO. 2) REGULATIONS (1986). HMSO, London