Silva, Rafael Rodrigues da, et al. “Effect of Crop Density of Two Genotypes of Maize in the Severity of Gray Leaf Spot and Yield in the Second Season Crop”. Semina: Ciências Agrárias, vol. 33, no. 4, Aug. 2012, pp. 1449-54, doi:10.5433/1679-0359.2012v33n4p1449.