Thanh V D, Thu N V and Preston T R 2012: Effect of potassium nitrate or urea as NPN source and levels of Mangosteen peel on in vitro gas and methane production using molasses, Operculina turpethum and Brachiaria mutica as substrate. Livestock Research for Rural Development. Volume 24, Article #63. Retrieved , from http://www.lrrd.org/lrrd24/4/thanh24063.htm