Post et al. (1990)
Also: Post et al. 1990
The global carbon cycle
Post, W. M., Peng, T. H., Emanuel, W. R., King, A. W., Dale, V. H., & DeAngelis, D. L. (1990). The global carbon cycle. American Scientist, 78(4), 310-326. Link to PDF
References
All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.