Nguyen Thiet,  Nguyen Thi Hong Nhan and Preston T R 2008 Enydra fluctuans and water spinach (Ipomoea aquatica) as agents to reduce pollution in pig waste water.  Proceedings MEKARN Regional Conference 2007: Matching Livestock Systems with Available Resources (Editors: Reg Preston and Brian Ogle), Halong Bay, Vietnam, 25-28 November 2007 http://www.mekarn.org/prohan/thie.htm