Mandl, Matthew, author
Prentice-Hall, 1967
Buku Teks
Rodiq, Oscar R., author
Fort Worth Saunders, 1990
Buku Teks
Bartholomew, David J., author
John Wiley & Sons, 1981
Buku Teks
Boulding, Kenneth E. (Kenneth Ewart), 1910-1993, author
Fefer and Simons , 1966
Buku Teks
Organisation for Economic Cooperation and Development , 1966
Buku Teks