Yehya, M. and 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), pp. 325–343. doi: 10.33899/tanra.2009.161841.