1. Anderson, E.G., Rizos, C., and Mather, R.S.: 1975. Unisurv G, 23, 23.
2. Barta, G.:1974. Satellite Geodesy and the International Structure of the Earth. Space Research, XIV. Akad. Verlag, Berlin.
3. Bursa, M: 1974. Proc. IAU Colloquium No. 26 on Reference Coordinate Systems in Earth Dynamics, Torun, Poland, 133.
4. Domaradzki, S., and Zielinski, J.B.:1979. Artificial Satellite, 14, 19.
5. Gaposchkin, E.M.:1973. Smithsonian Standard Earth III. Smithsonian Astrophysical Observatory, Cambridge, Massachusetts, Special Report No. 353.