Ferreira da Silva, Paulo Regis, et al. “Effect of Soil Management System and Fertilization Level on Sunflower Cultivated After Avena Strigosa”. Pesquisa Agropecuaria Brasileira, vol. 32, no. 6, June 1997, pp. 641-7, https://doi.org/10.1590/S1678-3921.pab1997.v32.4694.