Khongsud, Chalinee, Pipatpong sitkul, Panya Wongwitaya, and Saychol Sukyankij. “Effects of humic substance combination with nitrogen fertilizer on yield of water spinach and nitrogen activation coefficient in soil”. Journal of Applied Science and Innovation 1, no. 2 (September 22, 2026): No. 26206. accessed October 8, 2026. https://li02.tci-thaijo.org/index.php/jasi/article/view/1981.