1. Lemoine, F. G., et al., 1998, The development of the joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) geopotential model EGM96, NASA 206861, Goddard Space Flight Center.
2. Pavlis, N. K., S. A. Holmes, S. C. Kenyon, D. Schmidt, and R. Trimmer, 2005, A preliminary gravitational model to degree 2160, in, C. Jekeli, L. Bastos, and J. Fernandes, eds., Gravity, geoid, and space missions: Springer‐Verlag.