da Silva, P. R. F. and Nepomuceno, A. L. (1991) “Effect of plant arrangement on grain yield, yield components, oil content and weed control in sunflower”, Pesquisa Agropecuaria Brasileira, 26(9), pp. 1503–1508. doi: 10.1590/S1678-3921.pab1991.v26.3491.