U.S. Information Service,, 1981
Buku Teks
Herget, James E.
Texas: Rice University Press, 1990,
Buku Referensi
Horwitz, Morton J., author
Harvard University Press, 1977
Buku Teks
Current, Richard N., author
Alfred A. Knopf, 1965
Buku Teks
edited by Henry Steele Commager
Appleton-Century-Crofts, 1949
Buku Referensi