Kamm, Antony, author
Harper Collins Pub., 1993
Buku Referensi
editor, J.A.N. Lee
Fitzroy Dearborn, 1995
Buku Referensi
edited by Jack A. Goldstone, Ted Robert Gurr, Farrokh Moshiri
Westview Press, 1991
Buku Teks
Varga, Eugen, 1879-1964, author
Foreign Languages Publishing House, 1961
Buku Teks
Kohn, Hans, author
D. Van Nostrand, 1965
Buku Teks