1. H. Marschner, Mineral Nutrition of Higher Plants, London, 1995.
2. A. Krauss, Assessing soil potassium in view of contemporary crop production. Regional IPI-LIA-LUA Workshop on Balanced fertilization in contemporary plant production, Kaunas-Marijampol, Lithuania, 2003 (September 30 – October 1).
3. J.K. Syers, W. Sheldric, J. Lingard, Nutrient balance changes as an indicator of sustainable agriculture [C/CD]. in: Proceeding of the 17th World Congress of Soil Science, Bangkok, Thailand: WCSS, 2002 (1641-1/1641-10).
4. Effects of 50 years of fertilization with phosphorus and potassium on soil test levels and yields at locations;Cope;Soil Sci. Soc. Am. J.,1981
5. D.M. Oosterhuis, A post-mortem of the disappointing yields in the 1993 Arkansas cotton crop, in: D.M. Oosterhuis (Ed.), Proc. of the 1994 Cotton Research Meeting and Summaries of Cotton Research in Progress, Ark. Agri. Exp. Sta., Special Report, 1994, pp. 22–26.