1. P. Bonifazi, V. Ferrari, S. Frasca, G. V. Pallottino andG. Pizzella:Nuovo Cimento C,1, 465 (1978).
2. See, for instance,E. Amaldi andG. Pizzella:The search for gravitational waves, inRelativity, Quanta and Cosmology in the development of the scientific thought of A. Einstein, Johnson Reprint Corporation (Academic Press, New York, N. Y., 1979).
3. R. Ruffini andJ. A. Wheeler:Proceedings of the ESRO Colloquium (Interlaken, Switzerland, 1969);A. Degasperis:Lett. Nuovo Cimento,17, 36 (1976).
4. J. A. Tyson:Phys. Rev. Lett.,31, 326 (1973).
5. P. Bonifazi, E. Amaldi, G. V. Pallottino andG. Pizzella:Coincidences among the Louisiana, Stanford and Rome cryogenic gravitational wave antennas, inInternational Symposium on Experimental Gravitational Physics, Guangzhou, China, August 1987.