Yarber, Robert
Harper & Collins, 1993
Buku Teks
Hewings, Martin, author
Cambridge University Press , 2004
Buku Teks
Woods, Geraldine, author
John Wiley & Sons, 2016
Buku Teks
Kaplan, Jeffrey P., author
Prentice Hall International, 1995
Buku Teks
Jespersen, Otto, author
George Allen and Unwin, 1933
Buku Teks