General relativity and cosmology proceedings of the International School of Physics 'Enrico Fermi', course 47, Varenna on Lake Como, 30th June-12th July 1969
International School of Physics 'Enrico Fermi'47th1969Varenna.
Sachs, Rainer Kurt.
Società italiana di fisica.
New York London Academic Press
1971
Second title page in Italian. At head of title: Italian Physical Society
Relativity (Physics)