Khonpany Dounphady, Tasnee Attanandana, and Russell Yost. “Predicting Phosphorus Buffer Coefficients of Some Representative Soils for Maize Production in Lao PDR by Three Soil Analysis Methods”. Agriculture and Natural Resources, vol. 42, no. 5, Dec. 2008, pp. 27-33, https://li01.tci-thaijo.org/index.php/anres/article/view/244523.