Burayu Belew และ Worku. (2006) Conservation tillage options for sustainable crop production systems in the semi-arid and sub-humid oromiya /. Kasetsart University,:ม.ป.ท.Burayu Belew และ Worku. 2006. Conservation tillage options for sustainable crop production systems in the semi-arid and sub-humid oromiya /. ม.ป.ท.:Kasetsart University,;Burayu Belew และ Worku. Conservation tillage options for sustainable crop production systems in the semi-arid and sub-humid oromiya /. ม.ป.ท.:Kasetsart University, 2006. Print.