edited by Lawrence Butler and Harriet Jones
Heinemann , 1994
Buku Referensi
edited by Jack A. Goldstone, Ted Robert Gurr, Farrokh Moshiri
Westview Press, 1991
Buku Teks
Black, C.E.
Alfred A. Knopf, 1961
Buku Teks
Varga, Eugen, 1879-1964
Foreign Languages Publishing House, 1961
Buku Teks
Kohn, Hans
D. Van Nostrand, 1965
Buku Teks