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: Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., and Winiwarter, W. (2008).
How a century of ammonia synthesis changed the world. Nat. Geosci. 1, 636–639. doi: 10.1038/ngeo325