Kemp, David D.
Routledge, 1998
Buku Referensi
Allaby, Michael
Macmillan, 1991
Buku Referensi
Park, Chris
Oxford University Press, 2008
Buku Referensi
Allaby, Michael
Macmillan, 1985
Buku Referensi
London: Tiger Books International, 1994,
Buku Referensi