Baxter, R.R.
Harvard University Press, 1964
Buku Teks
Hollander, Barnett, author
Bowes & Bowes, 1965
Buku Teks
Slapper, Gary, author
Cavendish Publishing, 1999
Buku Teks
Backman, Jules
The Brookings Institution, 1943
Buku Teks
editor, Daniel Greenberg
Sweet & Maxwell, 2017
Buku Teks