Ruffini, R. (1975). Proceedings of the first marcel grossmann meeting on general relativity, organized and held at the international centre for theoretical physics, trieste and istituto di fisica teorica, University of Treiste 7-.. North-Holland Publishing.

Ruffini, R. Proceedings of the First Marcel Grossmann Meeting on General Relativity, Organized and Held at the International Centre for Theoretical Physics, Trieste and Istituto Di Fisica Teorica, University of Treiste 7-.. Amsterdam: North-Holland Publishing, 1975.

Ruffini, R. Proceedings of the First Marcel Grossmann Meeting on General Relativity, Organized and Held at the International Centre for Theoretical Physics, Trieste and Istituto Di Fisica Teorica, University of Treiste 7-.. North-Holland Publishing, 1975.