edited by Karl W. Deutsch and William J. Foltz
Atherton Press, 1966
Buku Teks
Huntington, Samuel P.
Vakils Feffer and Simons Private, 1968
Buku Teks
National Geographic Book Service
National Geographic Society, 1988
Buku Referensi
Orum, Anthony M.
Rowman & Littlefield Publishers, 1999
Buku Teks
Saaty, Thomas L.
Praeger, 1990
Buku Teks