Witman, Shepherd Luther, 1906-, author
Littlefield, Adams, 1963
Buku Teks
Bouquet, A.C., author
Penguin Books, 1953
Buku Teks
edited by Nathan Glick
United Sates Information Agency, 1989
Buku Teks
Schroeder, Richard C., author
International Communicational Agency, [date of publication not identified]
Buku Teks
United States Department of State, 1991
Buku Teks