Macedo, Fernando Giovannetti de, et al. “Accumulation and Availability Chromium, Cadmium and Lead in Soils Treated With Sewage Sludge for Eleven Consecutive Years”. Semina: Ciências Agrárias, vol. 33, no. 1, Apr. 2012, pp. 101-14, doi:10.5433/1679-0359.2012v33n1p101.