Todd, Paul, author
London : Balckstone, 1994,
Buku Referensi
by Paul A. Freund [and others]
Little, Brown, 1961
Buku Teks
by Paul A. Freund [and others]
Little, Brown, 1954
Buku Teks
Gardner, Simon
Clarendon Press, 1990
Buku Teks
Ramjohn, Mohamed
Cavendisch Publishing, 1998
Buku Teks