Amstrong, John A.
Colombia University Press, 1963
Buku Teks
Pergamon Press, 1978
Buku Teks
University League for Social Reform; edited by Peter Russell
McGraw-Hill, 1966
Buku Teks
Research Center for Peace and Unification, 1979
Buku Teks
Gellner, Ernest
Cornell University Press, 2008
Buku Teks SO