Povh, Fabrício Pinheiro, et al. “Behavior of NDVI Obtained from an Active Optical Sensor in Cereals”. Pesquisa Agropecuaria Brasileira, vol. 43, no. 8, Aug. 2008, pp. 1075-83, doi:10.1590/S1678-3921.pab2008.v43.194.