P. M. da Silveira, A. J. B. P. Braz, and A. D. Didonet, “Chlorophyll meter to evaluate the necessity of nitrogen in dry beans”, PAB, vol. 38, no. 9, pp. 1083–1087, Sep. 2003, doi: 10.1590/S1678-3921.pab2003.v38.6675.