Balláné Kovács, Andrea, et al. “Evaluation of KCl-EDTA-, CaCl2- DTPA-, CaCl2-DTPA-TEA Extractants for Estimating Available Cu in Soils”. Acta Agraria Debreceniensis, no. 27, Nov. 2007, pp. 5-9, https://doi.org/10.34101/actaagrar/27/3092.