Echer, Fábio Rafael, et al. “Potassium Sources in Covering Fertilization on Cotton I – Yield, Fiber Quality and Economic Analisys”. Semina: Ciências Agrárias, vol. 30, no. 4Sup1, Dec. 2009, pp. 1135-44, doi:10.5433/1679-0359.2009v30n4Sup1p1135.