Erviö, R. and Mäkitie, O. 1969. Studies on the effect of clay and organic matter contents on the determination of cation exchange properties in clay soils by the ammonium acetate and methylene-blue methods. Agricultural and Food Science. 41, 2 (May 1969), 73–81. DOI:https://doi.org/10.23986/afsci.71727.