Waugh, Anne
Churchill Livingstone, 2007
Buku Teks
Wilson, Kathleen J. W.
Churchill livingstone, 1998
Buku Teks
Cunningham, Daniel John
Oxford University Press, 1957
Buku Teks
Patton, Kevin T.
Elsevier Mosby, 2013
Buku Teks
Jackson, Sheila M.
The English Language Book, 1979
Buku Teks