Herget, James E., author
Texas: Rice University Press, 1990,
Buku Referensi
Herget, James E., author
Rice University Press, 1990
Buku Referensi
Duxbury, Neil, author
Clarendon Press, 1995
Buku Teks
Cowan, Thomas A.
Oceana Publications, Inc, 1967
Buku Teks
Curzon, L.B., author
CavendishPublishing Limited, 1992
Buku Teks