Gaya APA
Leo, S., Yugianingrum, I, G, C, I.
(2007).
English for academic purpose: essay writing
.
Yogyakarta:
.
Gaya MLA
Leo, Sutanto., Yugianingrum, I., Groth,, Cheryl, II..
"English for academic purpose: essay writing".
Yogyakarta:
,
2007.
.