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