(1)
El-Husseiny, O.; Abd-Elsamee, M.; Omara, I.; Fouad, A. Effect of Dietary Zinc and Niacin on Laying Hens Performance and Egg Quality. Int. J. Poult. Sci. 2008, 7 (8), 757–764. https://doi.org/10.3923/ijps.2008.757.764.