Sá Júnior, J. P. M. e, Uchôa, B. F. and Skogley, E. O. (2014) “Additions to the characterization and mapping of soils deficient in phosphorus and potassium, for corn, in the physiographic region of Northeast Brazil”, Pesquisa Agropecuaria Brasileira, 5(1), pp. 351–357. doi: 10.1590/S1678-3921.pab1970.v5.17755.