Ferreira, M. E., & Cruz, M. C. P. da. (1992). Selection of chemical extractors for the evaluation of availability of zinc in soils in the state of São Paulo, Brazil. Pesquisa Agropecuaria Brasileira, 27(2), 293–304. https://doi.org/10.1590/S1678-3921.pab1992.v27.3650