Kairbekov, Z., Ermoldina, E., Erezhep, N., Shingisova, R., & Myltykbaeva, Z. (2011). Chemical properties of humic acids. Chemical Bulletin of Kazakh National University, 64(4), 114-117. https://doi.org/https://doi.org/10.15328/chemb_2011_4114-117