Oxford University Press, 1950
Koleksi Publik
Westen, Drew
John Wiley & Sons, 2006
Buku Teks SO
chosen by Walter Murdoch and Alan Mulgan
Oxford University Press, 1950
Buku Teks
Edwards, Graham J.
McGraw-Hill, 1980
Buku Teks SO
Jones, David J.
Second Back Row Press, 1981
Buku Teks SO