Paust, Jordan J.
St. Paul Minn, 2000
Buku Teks
Wallace-Murphy, Tim
Watkins, 2006
Buku Teks
Trofimenko, Genrikh
Progress Publishers, 1986
Buku Teks
Bureau of International Information Programs United States Department of State, 2004
Buku Teks
Behrman, Jack N.
McGraw-Hill, 1971
Buku Teks