1. Exchangeable and acid-soluble potassium as regards availability and reciprocal relationships;Attoe,1945
2. Yield-of-phosphorus curves;Dean,1954
3. Determination of potassium deficient areas for cotton;De Frietas;Potash Rev.,1966
4. Comparison of methods of available potassium assessment for Eastern Nigeria soils;Ekpete;Soil Sci.,1972
5. A concept concerning the measurement of available soil nutrients;Fried;Soil Sci.,1952