S. M. B. de Oliveira e J. H. Larizzatti, “ Some observations on gold in the weathering profile at Garimpo Porquinho, an artisanal mine in the Tapajós Region, Brazilian Amazon ”, Geol. USP. Sér. Cient., vol. 5, nº 2, p. 1–11, mar. 2006, doi: 10.5327/S1519-874X2006000100001.