Primary: Congreves, K. A., Otchere, O., Ferland, D., Farzadfar, S., Williams, S., & Arcand, M. M. (2021, June 4).
Nitrogen Use Efficiency Definitions of Today and Tomorrow. Frontiers in Plant Science, 12.
https://doi.org/10.3389/fpls.2021.637108
Secondary: IAEA (1983). Guide on the Use of Nitrogen-15 and Radioisotopes in Studies of Plant Nutrition:
Calculations and Interpretation of Data. Vienna: IAEA.