Ribeirinho, Victor Sanches, et al. “SOIL FERTILITY, NUTRITIONAL STATUS, AND YIELD OF SUNFLOWER FERTILIZED WITH SEWAGE SLUDGE”. Pesquisa Agropecuária Tropical [Agricultural Research in the Tropics], vol. 42, no. 2, June 2012, pp. 166-73, https://doi.org/10.5216/pat.v42i2.15858.