Neptune, A.M.L. and Campanelli, A. 1980. Effects of different times and methods of ammonium sulphate-15N application and nitrogen-phosphorus 32P interaction on quantities and contents of N, P, K, in plant and leaf of maize, on yield,quantity of protein and efficiency of the nitrogen of the fertilizer and its conversion into protein . Anais da Escola Superior de Agricultura Luiz de Queiroz. 37, 2 (Jan. 1980), 1105–1143. DOI:https://doi.org/10.1590/S0071-12761980000200030.