Sweeney, Simon, author
Cambridge university press, 2010
Buku Teks
edited by Jack C. Richards
Longman, 1993
Buku Teks
Bender, Peter Urs, author
Gramedia Pustaka Utama, 1997
Buku Teks
Melde, Wilma
Naar, 1987
Buku Teks
Hughes, Rebecca, author
Pearson Education, 2002
Buku Teks