Castles, Stephen
Macmillan, 1993
Buku Teks
Birrell, Robert, author
Longman Cheshire, 1987
Buku Teks
Gollerkeri, Gurucharan, author
Oxford University Press, 2016
eBooks
Plane, David A., author
John Wiley & Sons, 1994
Buku Teks
Roberts, Stephen H.
Melbourne University Press, 1964
Buku Teks