NUVEL-1A Euler poles are defined in

• DeMets, C., R. G. Gordon, D. F. Argus, and S. Stein, Current plate motions, Geophys. J. Int., 101, 425-478, 1990.
• DeMets, C., R. G. Gordon, D. F. Argus, and S. Stein, Effect of recent revisions to the geomagnetic reversal time scale on estimate of current plate motions, Geophys. Res. Lett., 21, 2191-2194, 1994.
• http://dgfi2.dgfi.badw-muenchen.de/geodis/GDYN/nuvel1.html