Macmillan Press , 1976
Buku Teks
Nafziger, E. Wayne, author
Prentice-Hall, 1990
Buku Teks
Angelopoulos, Angelos
Preager, 1972
Buku Teks
Nafziger, E. Wayne, author
Cambridge University Press, 2006
Buku Teks
International Development Cooperation Agency, 1981
Buku Teks