Hall, B. D., Crotwell, A. M., Kitzis, D. R., Mefford, T., Miller, B. R., Schibig, M. F., and Tans, P. P.: Revision of the World Meteorological Organization Global Atmosphere Watch (WMO/GAW) CO2 calibration scale, Atmos. Meas. Tech., 14, 3015–3032, https://doi.org/10.5194/amt-14-3015-2021, 2021.
Hall, B. D., Crotwell, A. M., Miller, B. R., Schibig, M., and Elkins, J. W. (2019), Gravimetrically prepared carbon dioxide standards in support of atmospheric research, Atmos. Meas. Tech., 12, 517-524, 10.5194/amt-12-517-2019, 2019.