Vangnai, Somsak, Sawaeng Ruaysungnern, and Saipin Porntaveevatana. 1975. “Improved Growth Medium for Industrial Production of Rhizobium japonicum strain Soil-18”. Agriculture and Natural Resources 9 (2). Bangkok, Thailand:119-25. https://li01.tci-thaijo.org/index.php/anres/article/view/240718.