Cruz, Mara Cristina Pessôa da, and Manoel Evaristo Ferreira. “Selection of Methods for the Evaluation of Available Soil Copper”. Pesquisa Agropecuaria Brasileira, vol. 25, no. 4, Apr. 2014, pp. 647-59, doi:10.1590/S1678-3921.pab1990.v25.13477.