Sabaka, T., N. Olsen, R. H. Tyler, and A. Kuvshinov (2015), CM5, a pre-Swarm comprehensive geomagnetic field model derived from over 12 yr of CHAMP, Ørsted, SAC-C and observatory data,
Geophysical Journal International, 200, 1596-1626, doi:10.1093/gji/ggu493.