SEAMEO Regional Language Centre, 1982
Buku Referensi
Brown, Douglas, author
Pearson Longman, 2007
Buku Teks
Winasti Rahma Diani, author
2018
UI - Tesis (Membership)
Bloomfield, Leonard, author
Holt, Rinehart and Winston, 1961
Buku Teks
Beard, Adrian, author
Routledge, 2004
Buku Teks