Bauer, Lauria
London : Routledge, 1998
Buku Teks
Morgan, John, 1944-2004
Oxford University Press, 1990
Buku Teks SO
Jonathan Bradshaw and Roy Sainsbury, editors
Routledge, Taylor & Francis Group, 2019
Buku Teks
edited by David Kelleher and Sheila Hillier
Routledge, 1996
Buku Teks
Hyland, Ken
Longman, 2002
Buku Teks