1. R. Koop, R. Rummel, The future of satellite gravimetry, Final Report of the Future Gravity Mission Workshop, ESA/ESTEC, Noordwijk, The Netherlands, 12–13 April 2007
2. Laser Doppler interferometry mission for determination of the Earth’s Gravity Field, ESA Contract 18456/04/NL/CP, Final Report, Issue 1, 19 December 2005.
3. Laser interferometry high precision tracking for LEO, ESA Contract No. 0512/06/NL/IA, Final Report, July 2008.
4. System support to laser interferometry tracking technology development for gravity field monitoring, ESA Contract No. 20846/07/NL/FF, Final report, September 2008.
5. P.L. Bender, D.N. Wiese, R.S. Nerem, A possible dual-GRACE mission with 90 degree and 63 degree inclination orbits, in: Proceedings of the Third International Symposium on Formation Flying, Missions and Technologies, Noordwijk (NL), April 2008.