Melo, Ricardo Wanke de, et al. “Soybean Production Pointers in Rio Grande Do Sul Compared to the Agricultural Zoning”. Pesquisa Agropecuaria Brasileira, vol. 39, no. 12, Dec. 2004, pp. 1167-75, doi:10.1590/S1678-3921.pab2004.v39.6892.