Stebbins, Richard P., author
Harper & Row, 1963
Buku Teks
Reischauer, Edwin O., author
Alfred A. Knopf, 1968
Buku Teks
Millis, Walter
William Morrow & Company, 1947
Buku Teks
Brookings institution, 1949
Buku Teks
Seligman, Eustace, author
New York University Press, 1956.
Buku Teks