de Sá, N. M. H., Marriel, I. E. and Franco, A. A. (1994) “Variability in individual nodule activity of single strains of <i>Rhizobium etli</i> and R. <i>tropici in</i> symbiosis with <i>Phaseolus vulgaris</i>”;, Pesquisa Agropecuaria Brasileira, 29(12), pp. 1897–1904. doi: 10.1590/S1678-3921.pab1994.v29.4247.