Medeiros, João Carlos, et al. “Calcium:magnesium Ratio in Amendments of Soil Acidity: Nutrition and Initial Development of Corn Plants in a Humic Alic Cambisol”. Semina: Ciências Agrárias, vol. 29, no. 4, Aug. 2008, pp. 799-06, doi:10.5433/1679-0359.2008v29n4p799.