Mundstock, Claudio Mario, and Jeferson Zagonel. “Leaf Area Profile of Two Sunflower Cultivars under Different Rates and Timing of Nitrogen Application”. Pesquisa Agropecuaria Brasileira, vol. 29, no. 6, June 1994, pp. 847-51, doi:10.1590/S1678-3921.pab1994.v29.4124.