Gomes, J.B.V. et al. 1998. Soil profiles from three coastal plain regions. II. Dynamics of humic substances, iron and aluminum. Pesquisa Agropecuaria Brasileira. 33, 11 (Nov. 1998), 1921–1932. DOI:https://doi.org/10.1590/S1678-3921.pab1998.v33.5008.