Huntington, Samuel P.
Vakils Feffer and Simons Private, 1968
Buku Teks
Curtis, Sarah
Edward Arnold, 1996
Buku Teks
Orum, Anthony M.
Rowman & Littlefield Publishers, 1999
Buku Teks
Cambridge University Press, 1999
Buku Teks
Huntington, Samuel P.
Rajawali, 1983
Buku Teks