White, Ron, author
Prentice Hall International English Language Teaching , 1994
Buku Teks
Smith, Jennifer, author
Macmillan, 1982
Buku Teks
Gordon, Morton J.
Prentice-Hall, 1961
Buku Teks
Pearson Education Limited, 2010
Buku Referensi
Laws, Valerie
Buku Teks