Paengkoum, Siwaporn, Metha Wanapat, Chalong Wachirapakorn, and Ngarmnit Nontaso. 2013. “The Effect of Roughage and Urea Solution Infusion Levels on Ruminal NH3-N Concentration and Nutrient Digestibility in Beef Cattle and Swamp Buffaloes”. Science, Engineering and Health Studies 4 (1):47-55. https://doi.org/10.14456/sustj.2010.5.