REDDY, B G MASTHANA, and P S PATTAR. “Leaf Colour Chart-a Simple and Inexpensive Tool for Nitrogen Management in Transplanted Rice (Oryza Sativa)”. The Indian Journal of Agricultural Sciences, vol. 76, no. 5, Jan. 2011, https://epubs.icar.org.in/index.php/IJAgS/article/view/2871.