@ARTICLE {PLEYSIER:1988, title = {Extraction of potassium from some kaolinitic soils of the tropics}, author = {Pleysier, J. L. and Janssens, J. and Cremers, A. }, journal = {Soil Sci. Plant Anal.}, year = {1988}, volume = {19}, number = {1}, pages = {67--77}, }