Andrews, William G.
D.van Nostrand Company,Inc., 1968
Buku Teks
Petra Dobner, Martin Loughlin, editors
Oxford University Press, 2012
Buku Teks
Finer, S. E.
Clarendon Press Oxford, 1995
Buku Teks
Gibson, William M., author
Duke University Press, 1948
Buku Teks
Wheare, K. C., author
Oxford University Press, 1975
Buku Teks