“The Effect of Supplementation Urea and Sulfur in Mixed Cassava Waste Fermented and Soyabean Cake Waste on Digestibility of Protein and Blood Urea Male Sheep”. Animal Production: Indonesian Journal of Animal Production, vol. 1, no. 2, May 2011, https://doi.org/10.20884/1.jap.1999.1.2.19.