Rampim, Leandro, et al. “Available Phosphorus and Sulphur, Exchangeable Aluminum and Remaining Phosphorus in Rhodic Eutrudox Submitted to Gypsum Cultivated With Wheat and Soybean”. Semina: Ciências Agrárias, vol. 34, no. 4, Aug. 2013, pp. 1623-38, doi:10.5433/1679-0359.2013v34n4p1623.