Berta-Szabó, Emese, et al. “Effects of Long-Term K Fertilization and Liming on the Extractable and Exchangeable K Contents of a Haplic Phaeosem Soil”. Acta Agraria Debreceniensis, no. I, Oct. 2010, pp. 141-5, https://doi.org/10.34101/actaagrar/I/8392.