Robert, Collins, author
Harper Collins, 1995
Buku Referensi
Brown, L. Neville (Lionel Neville), author
Clarendon Press, 1998
Buku Teks
Carre, Jean Jacques, author
Stanford University Press, 1975
Buku Teks
Daniels, May
Edinburgh : At The University Press, 1953
Buku Teks
Gershoy, Leo, author
Appleton Century Crofts, 1938
Buku Teks