Ditthakit, P., and J. Singkham. “The Use of Modified Leonardite for Water Convolvulus Growing in Clay Soil”. STOU Journal of Agriculture (Online), vol. 1, no. 1, June 2019, pp. 47-56, https://so01.tci-thaijo.org/index.php/stouagjournal/article/view/246567.