Adhikary, B. H., S. Vangnai, T. Attanandana, P. Swatdee, and P. Sripichitt. “Growth and Nitrogen Production Rates of Azolla ( Azolla microphylla ) as Affected by Its Cultivation Methods : An Economic Perspective in Rice Cultivation in Thailand”. Agriculture and Natural Resources, vol. 31, no. 1, Mar. 1997, pp. 134-40, https://li01.tci-thaijo.org/index.php/anres/article/view/240797.