Cooper, Robert L.
Cambridge University Press, 1989
Buku Teks SO
edited by Michael Kirkwood
Macmillan, 1989
Buku Teks SO
Graduate School of Language and Culture, Osaka University, 2018
Majalah, Jurnal, Buletin
Christie, Francis
Oxford University Press, 1989
Buku Teks SO
SEAMEO Regional Language Centre, 1983
Buku Referensi