Suwanarit, A., N. Lekhasoonthrakorn, J. Rungchuang, and S. Kritapirom. “Effects of Intercropping Groundnut and Green-Manure Legumes to Corn on the Yields of Corn and Productivity and Chemical Properties of Soil”. Agriculture and Natural Resources, vol. 32, no. 3, Sept. 1998, pp. 374-8, https://li01.tci-thaijo.org/index.php/anres/article/view/240586.