Gaya APA
Betsis, A., Mamas, L. (2016).
Succeed in IELTS: Self-practice, Authentic test format, Practical usage .
Jakarta:
Erlangga.
Gaya MLA
Betsis, Andrew., Mamas, Lawrence.
"Succeed in IELTS: Self-practice, Authentic test format, Practical usage".
Jakarta:
Erlangga,
2016.
Buku.