Bech, J., Ugalde, S., Roca, N., Tonon, L., Larriva, G., & Sokolovska, M. (2011). Concentration and distribution of heavy metals in Andisols and Vertisols of the Azuay Andes (Equador). International conference "100 soil science in Bulgaria", 16-20 may, 2011, Sofia, Bulgaria. с. 59-64.