Cleveland, C. C., Townsend, A. R., Schimel, D. S., Fisher, H., Howarth, R. W., Hedin, L. O., Perakis, S. S., Latty, E. F.,
Von Fischer, J. C., Elseroad, A., & Wasson, M. F. (1999). Global patterns of terrestrial
biological nitrogen (N2) fixation in natural ecosystems. Global Biogeochemical Cycles,
13(2), 623-645. doi:10.1029/1999GB900014.