Jayarajah, Carl, author
World Bank, 1996
Buku Teks
edited by James F. Short
Sage, 1986
Buku Teks
Gilbert, Neil, author
Prentice-Hall, 1986
Buku Teks
Gilbert, Neil, author
Allyn and Bacon, 1998
Buku Teks
Gilbert, Neil, author
Prentice-Hall, 1974
Buku Teks