Stamford, Newton Pereira. “Quick Method for Identification of Inoculation Nodules, Efficiency of N2 Fixation and Cross Inoculation of Tropical Legumes”. Pesquisa Agropecuaria Brasileira, vol. 23, no. 4, Apr. 2014, pp. 357-62, doi:10.1590/S1678-3921.pab1988.v23.13857.