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2. 1. Barthelmes, F.: Local gravity field approximation by point masses with optimized positions. Proceedings of the 6th International Symposium "Geodesy and Physics of the Earth", GDR, Potsdam, August 22-27, 1988
3. 2. Veröff. Zentralinst. Physik der Erde Nr. 102, Part 2, Potsdam 1989
4. Dietrich, R.; Gendt, G.: A gravity field model from LAGEOS based on point masses (POEM-L1). Proceedings of the 6th International Symposium “Geodesy and Physics of the Earth”, GDR, Potsdam, August 22–27, 1988; Veröff. Zentralinst. Physik der Erde Nr. 102, Part 2, Potsdam 1989
5. Dietrich, R.; Gendt, G.; Barthelmes, F.: Geodynamic Research using LAGEOS Laser Ranging Data at the Central Institute for Physics of the Earth Potsdam (GDR). Paper presented at the IAG General Meeting Edinburgh, Scotland, August 3–12, 1989