Mann et al. (1999)
Also: Mann et al. 1999
Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations
Mann, M. E., Bradley, R. S., & Hughes, M. K. (1999). Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical research letters, 26(6), 759-762. Link to PDF
https://doi.org/10.1029/1999GL900070
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.