Santos, Henrique Pereira dos, et al. “Economic Analysis of Crop Rotation Systems for Wheat, over a Two-Year Period, under No-Tillage”. Pesquisa Agropecuaria Brasileira, vol. 32, no. 11, Nov. 1997, pp. 1111-7, doi:10.1590/S1678-3921.pab1997.v32.4759.