Herget, James E.
Rice University Press, 1990
Buku Referensi
Duxbury, Neil
Clarendon Press, 1995
Buku Teks
Cowan, Thomas A.
Oceana Publications, Inc, 1967
Buku Teks
Curzon, L.B.
CavendishPublishing Limited, 1992
Buku Teks
Wacks, Raymond
Blackstone Press limited, 1999
Buku Teks