1. Arnold, P. W., Potassium-supplying power of some British Soils. Nature187, 4735, 436?437 (1960).
2. Caillère, S., Hénin, and Meriaux, S., Transformation experimentale d'une montmorillonite en une phyllite a 10 A type illite. Comp. Rend.226, 680?681 (1948).
3. Grim, R. E., Clay Mineralogy. McGraw-Hill Book Co. Inc. p. 68?69 (1953).
4. Joffe, J. S. and Levine, A. K., Fixation of potassium in relation to exchange capacity of soils. III Factors contributing to the Fixation Process. Soil Sci.63, 241?247 (1947).
5. Marel, H. W. van der, Potassium fixation in Dutch soils. Mineralogical analyses. Soil Sci.78, 163?179 (1954).