Richards, Michael D, author
John Wiley & Sons, 2014
Buku Teks
Palmer, Alan, author
Penguin Books , 1987
Buku Referensi
edited by Peter Duus
Cambridge University Press, 1995
Buku Referensi
Reese, Trevor R.
F.W. Cheshire, 1964
Buku Teks
Simpson, W.O.
Stanley Thornes, 1988
Buku Teks