Christensen, Howard B., author
Hoghton Mifflin, 1977
Buku Teks
Sartika Kurniali, author
PT Gramedia, 2009
Buku Teks
Ministry of Foreign Affairs and Trade, 1996
Buku Teks
Drago, Carl, author
Blackwell Publishing, 2007
Buku Referensi
Kemp, Marwin K., 1942-, author
Academic Press, c1979
Buku Teks