“A 15N Tracer Study to Evaluate the Effects of Nitrogen and Copper Fertilization on Fertilizer Nitrogen Efficiency in Rice Production: 15N Tracer Study for N and Cu Fertilization in Rice”, Pakistan Journal of Scientific & Industrial Research, vol. 52, no. 1, pp. 53–58, Feb. 2009, Accessed: Mar. 10, 2026. [Online]. Available: https://www.v2.pjsir.org/index.php/biological-sciences/article/view/510