Zimmermann, Francisco José Pfeilsticker, and Armando Conagin. “Fitness of 2nd Degree Polinomials Models in Fertilizer Research”. Pesquisa Agropecuaria Brasileira, vol. 21, no. 9, Apr. 2014, pp. 971-8, doi:10.1590/S1678-3921.pab1986.v21.15012.