Regional Office for the Western Pacific, 1993
Buku Teks
Laudon, Kenneth C., 1944-, author
Prentice-Hall, 2001
Buku Teks
Hatch, Mary Jo
Oxford University Press, 1997
Buku Teks
French, Wendell L., author
Prentice-Hall International, 1990
Buku Teks
Caplo, Theodore, author
Harcourt, Brace & World, 1964
Buku Teks