Laski, Harold J., author
Manchester University Press, 1951
Buku Teks
Bennett, Martyn
Routledge, 2000
Buku Teks
editor, Brian J. Rusbridge
Municipal Journal Limited, 1995
Buku Referensi
Backman, Jules
The Brookings Institution, 1943
Buku Teks
Jackson, David, author
LLoyd's of London Press, 1987
Buku Teks