Birdsall, Stephen S.
John Wiley & Sons, 1992
Buku Teks SO
editor, Kathleen E. Hug; penerjemah, Sumantri Ar.
Office of International Infrmation Programs US Department of State, [date of publication not identified]
Buku Teks SO
[publisher not identified], [date of publication not identified]
Buku Teks
[Publisher not identified], [Date of publication not identified]
Buku Teks
McCan, Robert L.
Dinas Penerangan Amerika Serikat Kedutaan Besar Amerika Serikat, 1991
Buku Teks SO