Xaysatith Souliyavongsa และ Tasnee Attanandana. (2010) Phosphorus requirements for maize in ultisols of Xiengkhouang province, Lao PDR. Kasetsart University,:ม.ป.ท.Xaysatith Souliyavongsa และ Tasnee Attanandana. 2010. Phosphorus requirements for maize in ultisols of Xiengkhouang province, Lao PDR. ม.ป.ท.:Kasetsart University,;Xaysatith Souliyavongsa และ Tasnee Attanandana. Phosphorus requirements for maize in ultisols of Xiengkhouang province, Lao PDR. ม.ป.ท.:Kasetsart University, 2010. Print.