Ferguson, Gibson, author
Edinburgh University Press, 2006
Buku Teks
Cooper, Robert L., author
Cambridge University Press, 1989
Buku Teks
Graduate School of Language and Culture, Osaka University, 2018
Majalah, Jurnal, Buletin
Christie, Francis
Oxford University Press, 1989
Buku Teks
SEAMEO Regional Language Centre, 1983
Buku Referensi