Phommasack Outhen, T R Preston T R and Leng R A 2011 Effect of supplementation with urea or calcium nitrate and cassava leaf meal or fresh cassava leaf in an in vitro fermentation using a basal substrate of sugar cane stalk.  Livestock Research for Rural Development. Volume 23, Article #023. Retrieved , from http://www.lrrd.org/lrrd23/2/outh23023.htm