Hang Du Thanh, Linh Nguyen Quang, Preston T R , Everts H and Beynen A C 2009: Effect of supplementary DL-methionine in pig diets with cassava leaves as a major protein source. Livestock Research for Rural Development. Volume 21, Article #15. Retrieved , from http://www.lrrd.org/lrrd21/1/hang21015.htm