Partelli, Fábio Luiz, et al. “Comparison of Two DRIS Methods for Diagnosing Nutrients Deficiencies in Coffee Trees”. Pesquisa Agropecuaria Brasileira, vol. 41, no. 2, Feb. 2006, pp. 301-6, doi:10.1590/S1678-3921.pab2006.v41.7137.