Inthapanya Sangkhom,  Kongvongxay Siton and Preston T R 2012 Effect of supplements of Tithonia diversifolia, and potassium nitrate or urea, on methane production in an in vitro system using sugar cane stalk as energy source.  Proceedings of the International Conference "Livestock-Based Farming Systems, Renewable  Resources and the Environment", 6-9 June 2012, Dalat, Vietnam (Editors: Reg Preston and Sisomphone Southavong) http:/www.mekarn.org/workshops/dalat2012/html/sangsiton.htm