Amaefule K U, Ojewola G S and Uchegbu E C  2004: The effect of methionine, lysine and/or vitamin C (ascorbic acid) supplementation on egg production and egg quality characteristics of layers in the humid tropics. Livestock Research for Rural Development. Vol. 16, Art. #64. Retrieved , from http://www.lrrd.org/lrrd16/9/amae16064.htm