D. Nadalia, A. Hartono, H. B. Pulunggono, B. H. Trisasongko, W. Widiatmaka, and M. F. Emzir, “Modeling the activity ratio of soil potassium using machine learning approach”, Sains Tanah J. Soil Sci. Agroclimatology, vol. 22, no. 2, pp. 243–254, Oct. 2025, doi: 10.20961/stjssa.v22i2.100102.