1. Official Methods of Analysis,1975
2. Dean, W. F., 1978. Nutrient requirements of ducks. Pages 132–140 in Proc. Cornell Nutr. Conf.
3. Nutritional studies with the ducks;Hegsted;III. Niacin deficiency. J. Nutr.,1946
4. Studies in duck nutrition;Heuser;5. Bowed legs in ducks, a nutritional disorder. Poultry Sci.,1953
5. The determination of tryptophan in purified proteins and in feedingstuffs;Matheson;Br. J. Nutr.,1974