Mengistu, F., Davtyan, A., Vorster, I., Xuecheng, D., Sembiring, E., GasmElseed, Y. and Bashir, A. 2004. System approach problem diagnosis and development strategies for a competitive mandarin to industry in the Karo highlands, North Sumatra, Indonesia. Uganda Journal of Agricultural Sciences. 9, 1 (Oct. 2004), 7–16.