1. Proceed. IAG Symp. No. 116, Global Gravity Field and Its Temporal Variations, Boulder, Co., USA;OB Andersen,1996
2. Brennecke, J., D. Lelgemann, W. Torge, H.-G. Wenzel (1983). A European astro-gravimetric geoid. Deutsche Geod. Komm., Reihe B, Nr. 269, Frankfurt/Main.
3. IAG Symp. No. 113, Gravity and Geoid, Graz, Austria;H Denker,1994
4. IAG Symp. No. 117, Gravity, Geoid and Maine Geodesy, Tokyo, Japan;H Denker,1997
5. Proceed. IAG Symp. No. 117, Gravity, Geoid and Maine Geodesy, Tokyo, Japan;F Lemoine,1997