Tran Hoang Chat, Ngo Tien Dung, Dinh Van Binh and Preston T R 2005: Effect on yield and composition of water spinach (Ipomoea aquatica), and on soil fertility,  of fertilization with worm compost or urea. Workshop-seminar "Making better  use of local feed resources" (Editors: T R Preston and Brian Ogle). MEKARN-CTU, Cantho, 23-25 May, 2005, Article # 47.  Retrieved , from http://www.mekarn.org/proctu/chat47.htm