Leal, M. A. de A. and Penteado, A. de F. (1994) “Efficiency of nonparametric methods for the analysis of the nodulation capacity of a leguminous crop”, Pesquisa Agropecuaria Brasileira, 29(2), pp. 177–182. doi: 10.1590/S1678-3921.pab1994.v29.4042.