Yehya, M., & Abdullah, M. (2009). The Use of (2SLS) and (3SLS) Methods to Estimate the Simultaneous Equations System of the World Prices of the Grains for the Period (1961-2002). TANMIYAT AL-RAFIDAIN, 31(93), 325–343. https://doi.org/10.33899/tanra.2009.161841