MuhammadH., SabihamS., RachimA., and AdijuwanaH. “The Rate of S-Element Transformation to Sulfate on Three Kinds of Soils With and Without Addition of Organic Matter”. Jurnal Ilmu Tanah Dan Lingkungan, Vol. 7, no. 1, Apr. 2005, pp. 15-21, doi:10.29244/jitl.7.1.15-21.