edited by Kathleen E. Hug
Office of International Infrmation Programs US Department of State, [Date of publication not identified]
Buku Teks SO
Gultom, Samuel
Greenwood Press, 1987
Buku Referensi
Office of International Information Programs, 1991
Buku Teks SO
edited by Nathan Glick
United Sates Information Agency, 1989
Buku Teks
Birdsall, Stephen S.
John Wiley & Sons, 1992
Buku Teks SO