Farmer, David Hugh, author
Oxford University Press, 1992
Buku Referensi
Cunningham, Lawrence, author
BlackWell, 2004
Buku Teks
Duchet-Suchaux, Gaston, author
Flammarion, 1994
Buku Referensi
Cecil, Lord David
Clarendom Press, 1951
Buku Teks
Knowles, David, author
At University Press, 1963
Buku Teks