Martin Montgomery ... [and others]
Routledge , 2007
Buku Teks
West, Michael
Longmans, Green and Co., 1951
Buku Teks
Andari Ditya, author
Universitas Indonesia, 2013
UI - Makalah dan Kertas Kerja
Murphy, Raymond, author
Cambridge University Press, 1998
Buku Teks
Hewings, Martin, author
Cambridge University Press, 2005
Buku Teks