Bullock, Barbara, author
Lippincott , 2000
Buku Teks
Berman, Harold J., author
Little, Brown, 1953
Buku Teks
Ministry of Foreign Affairs Netherlands, Communication Division (DVL/VB) ,
Buku Teks
Hahn, Dale B., author
McGraw-Hill, 2002
Buku Teks
Hahn, Dale B.
McGraw-Hill, 2003
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