Columbia subject headings:
Authors, Spanish--Correspondence.
Personal correspondence.
Philosophers--Spain--Correspondence.
Unamuno, Miguel de, 1864-1936--Correspondence.
Harvard subject headings:
Authors, Spanish--Correspondence.
Philosophers--Spain--Correspondence.
Unamuno, Miguel de, 1864-1936. Correspondence.
Princeton subject headings:
Authors, Spanish--Correspondence.
Philosophers--Spain--Correspondence.
Unamuno, Miguel de, 1864-1936--Correspondence.