Nguyen Huu Yen Nhi and Preston T R 2012  Growth of red tilapia (Oreochomis mossambicus) and black tilapia (Oreochomis niloticus) with common carp (Ciprinus carpio) in monoculture and polyculture by using natural feed in organic fertilizer pond from biodigester effluent. 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/nhi.agu2.htm