Souza, Luiz Augusto Gomes de, et al. “Development and Natural Nodulation of Legume Trees in Soils from Pernambuco, Brazil”. Pesquisa Agropecuaria Brasileira, vol. 42, no. 2, Feb. 2007, pp. 207-1, doi:10.1590/S1678-3921.pab2007.v42.7554.