Inamdar, Ashpak, et al. “Determination of Humic Acid and Fulvic Acid by Spectrophotometric Analysis from the Effervescent Tablet”. International Journal of Recent Advances in Multidisciplinary Topics, vol. 2, no. 11, Nov. 2021, pp. 144-50, https://journals.ijramt.com/index.php/ijramt/article/view/1549.