de Sá, N.M.H. et al. 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 (Dec. 1994), 1897–1904. DOI:https://doi.org/10.1590/S1678-3921.pab1994.v29.4247.