Moro, Edemar, et al. “Soil Acidity As Affecting Micronutrients Concentration, Nitrato Reductase Enzyme Activity and Yield in Upland Rice Plants”. Semina: Ciências Agrárias, vol. 34, no. 6Supl1, Dec. 2013, pp. 3397-10, doi:10.5433/1679-0359.2013v34n6Supl1p3397.