Noor, Abdun, author
World Bank, 1981
Buku Teks
Robertson, Cathie, 1946-, author
Wadsworth and Cengage Learning, 2013
Buku Teks
Prentice-Hall, 1984
Buku Teks
Longres, John F.
F.E. Peacock Publisher, Inc, 1990
Buku Teks
Stone, Christopher D.
Harper & Row , 1975
Buku Teks