Zimmermann, Francisco José Pfeilsticker, and Armando Conagin. 2014. “Fitness of 2nd Degree Polinomials Models in Fertilizer Research”. Pesquisa Agropecuaria Brasileira 21 (9): 971-78. https://doi.org/10.1590/S1678-3921.pab1986.v21.15012.