Bendix, Reinhard, author
John Wiley, 1964
Buku Teks
edited by Karl W. Deutsch and William J. Foltz
Atherton Press, 1966
Buku Teks
Huntington, Samuel P., author
Vakils Feffer and Simons Private, 1968
Buku Teks
National Geographic Book Service
National Geographic Society, 1988
Buku Referensi
Orum, Anthony M., author
Rowman & Littlefield Publishers, 1999
Buku Teks