Columbia subject headings:
Education--Philosophy.
Giner de los Ríos, Francisco, 1839-1915.
Unamuno, Miguel de, 1864-1936.
Harvard subject headings:
Authors, Spanish--20th century--Correspondence
Giner de los Ríos, Francisco, 1839-1915.
Unamuno, Miguel de, 1864-1936. Correspondence.
Princeton subject headings: