Graves, Jonathan
Longman, 1996
Buku Teks
Dea Amelia, author
Universitas Indonesia, 2011
UI - Skripsi (Open)
Rifka Sofianita, author
2019
UI - Tesis (Membership)
Whitman, Jim, author
Routledge, 2005
Buku Teks
Huxham, Mark
Prentice-Hall, 2000
Buku Teks