Zilli, Jerri Édson, et al. “Symbiotic Efficiency of Cowpea Bradyrhizobium Strains in Cerrado Soils”. Pesquisa Agropecuaria Brasileira, vol. 41, no. 5, May 2006, pp. 811-8, https://doi.org/10.1590/S1678-3921.pab2006.v41.7210.