Matos, V. P., Silva, R. F. da, Vieira, C., & Silva, J. F. da. (1991). Critical period of competition between weeds and cowpea. Pesquisa Agropecuaria Brasileira, 26(5), 737–743. https://doi.org/10.1590/S1678-3921.pab1991.v26.3398