Jones, Maldwyn Allen
University of Chicago Press, 1960
Buku Teks SO
Russel Sage Foundation, 2000
Buku Teks
Supperstone, Michael
Longman, 1994
Buku Teks SO
Warr, George
Sweet & Maxwell, 1994
Buku Teks SO
Bruce, J. Campbell
Random House , 1954
Buku Teks SO