Moreira, Maurício Alves. “Direct Expansion Method for Estimating Soybean and Corn Area through Multitemporal and Espectral LANDSAT TM1 Data”. Pesquisa Agropecuaria Brasileira, vol. 26, no. 10, Oct. 1991, pp. 1607-13, doi:10.1590/S1678-3921.pab1991.v26.3503.