Fixsen (2009)
Also: Fixsen 2009
The temperature of the cosmic microwave background
Fixsen, D. J. (2009). The temperature of the cosmic microwave background. The Astrophysical Journal, 707(2), 916. Link to PDF
http://dx.doi.org/10.1088/0004-637X/707/2/916
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.