A. Sajjad, A., A. Mahmud, M. Akram, A. Khalique, F. Hussnain, A. S. Haidary, U. Khan, and M. Usman. 2013. “Effect of Dietary Supplementation of Different Lutein Sources on the Productive Performance of Commercial Layers Categorized in Three Body Weights”. Scientific Journal of Zoology 2 (6):64-73. http://www.sjournals.com/index.php/sjz/article/view/1165.