B.O. Al- Jaff, “USING CENTER OF GRAVITY EQUATION FOR MICA AND SMECTITE IN EVALUATION OF K-STATUS IN SOME SOILS OF IRAQI KURDISTAN REGION”, Iraqi J. Agric. Sci., vol. 55, no. 3, pp. 1110–1119, Jun. 2024, doi: 10.36103/w953r397.