P. E. Gazel Teixeira, A. R. Fernandes, J. R. Galvão, W. V. da Silveira Pereira, S. R. Almeida Casanova, e P. P. da Costa Alves Filho, “Cowpea yield on soils with residues of NPK and natural phosphate fertilizers in succession the area of degraded pasture”, Revista Ceres, vol. 63, nº 4, set. 2016.