Vernon Bogdanor
Clarendon Press Oxford, 1995
Buku Teks
Finer, S. E.
Clarendon Press Oxford, 1995
Buku Teks
Rudden, Bernard
Clarendon Press Oxford, 1995
Buku Teks
Andrews, William G.
D.van Nostrand Company,Inc., 1968
Buku Teks
Gibson, William M., author
Duke University Press, 1948
Buku Teks