1. Bender, P. L.: 1972,Memorandum to Members of the COSPAR ? IAU ? IUGG. Working Party on Lunar Laser Ranging.
2. Bonatz, M., Melchior, P. J., and Ducarme B.: 1971,Obs. Roy. Belg. Bull. Obs. Marées Terrestres 4, 1
3. Bower, D. R.: 1970,Obs. Roy. Belg. Comm. A9;Série Geophys. 96, 106.
4. Caputo, M.: 1961,J. Geophys. Res. 66, 1479.
5. Djurovic, D. and Melchior, P.: 1973Obs. Roy. Belg. Comm. B79,Série Geophys. 115.