Dias, Kaio Gonçalves de Lima, et al. “Alternative Sources of Potassium in Coffee Plants for Better Soil Fertility, Productivity, and Beverage Quality”. Pesquisa Agropecuaria Brasileira, vol. 53, no. 12, Dec. 2018, pp. 1355-62, doi:10.1590/S1678-3921.pab2018.v53.25965.