Iv Sophea and Preston T R 2010 Effect of different levels of supplementary potassium nitrate replacing urea on growth rates and methane production in goats fed rice straw, mimosa foliage and water spinach. International Conference on Livestock, Climate Change and Resource Depletion,   (Editor: Reg Preston),  Champasack University, Pakse, LAO PDR, 9-11 November 2010 . httm://www.mekarn.org/workshops/pakse/html/soph.htm