United States Information Agency, 1987
Buku Teks
Board of Trusless, 1960
Buku Referensi
Whitaker,Arthur P.
Harvard University Press, 1948
Buku Teks
The America University, [date of publication not identified]
Buku Teks
Bemis, Samuel Flagg, 1891-1973, author
Harcourt, Brace, 1943
Buku Teks