Dang Thi My Tu, Nguyen Thi Kim Dong and Preston T R 2011 Effect on duckweed composition of different levels of biodigester effluent in the growth medium and of transferring nutrient-rich duckweed to nutrient-free water. Workshop on Reducing Greenhouse Gas Emissions from Livestock and Soils (Editors: Reg Preston and Sisomphone Southavong). National Institute of Animal Science, Hanoi, 14-15 November 2011. httm://www.mekarn.org/workshops/GHG-CC/mytu.htm