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2. Bank of Sudan (1988), Bank of Sudan Twenty Eighth Annual Report 1987, Bank of Sudan, Khartoum.
3. LEEC Discussion Paper 90-03;E. B. Barbier,1990
4. BarbierE. B., A.Markandya, and D. W.Pearce (1990), ?Sustainable Agricultural Development and Project Appraisal?, European review of Agricultural Economics 17, 181?196.
5. International Institute for Environment and Development (IIED) and Institute for Environmental Studies (IES) (1990), Gum Arabic Rehabilitation in the Republic of Sudan: Stage I Report, IIED, London.