M.R. UMESH, et al. “ Optimization of Nitrogenous Fertilizers Using Leaf-Colour Chart for Irrigated Hybrid Maize (Zea Mays) Grown in Vertisol of Sub-Tropical India”. Indian Journal of Agronomy, vol. 65, no. 1, Oct. 2001, pp. 77-82, https://doi.org/10.59797/ija.v65i1.2952.