Sfredo, G.J., et al. “ Absorption of Nutrients by Two Cultivars of Sunflower Plants (Helianthus Annus L.) under Field Conditions: III. Acumulation of the Macronutrients ”. Anais Da Escola Superior De Agricultura Luiz De Queiroz, vol. 40, no. 2, Jan. 1983, pp. 1189-18, https://doi.org/10.1590/S0071-12761983000200021.