Columbia subject headings:
Cosmology.
Einstein, Albert, 1879-1955.
Relativity (Physics)
Sitter, Willem de.
Harvard subject headings:
Cosmology.
Einstein, Albert, 1879-1955
Relativity (Physics)
Sitter, Willem de.
Princeton subject headings:
Cosmology.
Einstein, Albert, 1879-1955.
Relativity (Physics)
Sitter, Willem de.