Farmer, David Hugh, author
Oxford University Press, 1992
Buku Referensi
Wade, Terence
New York : Oxford University Press, 2002
Buku Referensi
Blackburn, Simon, author
Buku Referensi
edited by Colin Howlett
Oxford University Press, 1996
Buku Referensi
edited by P. S. Falla
Clarendon Press, 1990
Buku Referensi