Rodriguez-Moreno, F., and F. Llera-Cid. “Evaluating Spectral Vegetation Indices for a Practical Estimation of Nitrogen Concentration in Dual-Purpose (forage and Grain) Triticale”. Spanish Journal of Agricultural Research, Vol. 9, no. 3, Aug. 2011, pp. 681-6, doi:10.5424/sjar/20110903-265-10.