Salgado, Ailena Sudo, et al. “Intercropping of Lettuce-Carrot and Lettuce-Radish under Organic Management”. Pesquisa Agropecuaria Brasileira, vol. 41, no. 7, July 2006, pp. 1141-7, doi:10.1590/S1678-3921.pab2006.v41.7257.