Hall, Peter
Blackwell, 2002
Buku Teks
edited by Jack A. Goldstone, Ted Robert Gurr, Farrokh Moshiri
Westview Press, 1991
Buku Teks
Varga, Eugen, 1879-1964
Foreign Languages Publishing House, 1961
Buku Teks
Kohn, Hans
D. Van Nostrand, 1965
Buku Teks
Urwick, Lyndall F.
Pitman Publishing Corporation , 1958
Buku Teks