Rao, M.R. and Morgado, L.B. 2014. A review of maize-beans and maize-cowpea intercrop systems in the semiarid northeast Brazil. Pesquisa Agropecuaria Brasileira. 19, 2 (Apr. 2014), 179–192. DOI:https://doi.org/10.1590/S1678-3921.pab1984.v19.15374.