1. Department of Agriculture. (2014). World Agriculture Supply and Demand Estimate Report. Washington, DC: UASD.
2. Director of Economics. (2015). Publication January 2015. Director of Economics and Statastics.
3. Elmasri, R., & Navathe, S. B. (2011). Fundamentals of database system (6th. ed.). Boston: Pearson Education, Inc.