A. Marais, E. Kotzé, J. Labuschagne, L. Visser, and C. D. Morris, “Proposed adaptation of the KMnO4 oxidation method for determining active carbon for South African soils”, S. Afr. J. Sci., vol. 116, no. 1/2, Jan. 2020, doi: 10.17159/sajs.2020/6443.