Nachtigall, Gilmar Ribeiro, et al. “Forms of Copper in Vineyard Soils As Affected by PH and Poultry Litter Application”. Pesquisa Agropecuaria Brasileira, vol. 42, no. 3, Mar. 2007, pp. 427-34, doi:10.1590/S1678-3921.pab2007.v42.7584.