Schroeder, Richard C.
International Communicational Agency, [date of publication not identified]
Buku Teks SO
Gultom, Samuel
Greenwood Press, 1987
Buku Referensi
United States Information Agency, 1991
Buku Teks SO
Office of International Information Programs, 1991
Buku Teks SO
Birdsall, Stephen S.
John Wiley & Sons, 1992
Buku Teks SO