Embassy of the United States of American, [date of publication not identified]
Buku Teks
United States Information Agency, 1991
Buku Teks
edited by Nathan Glick
United Sates Information Agency, 1989
Buku Teks
United State Information Agency, 1994
Buku Teks
Gultom, Samuel
Greenwood Press, 1987
Buku Referensi