Li*, H., Y. Li, and C. Li. “Characterization of Humic Acids and Fulvic Acids Derived from Sewage Sludge”. Asian Journal of Chemistry 25, no. 18 (December 12, 2013): 10087–10091. Accessed August 26, 2024. https://asianpubs.org/index.php/ajchem/article/view/25_19_14.