Gaya APA
Azar, B, S. (2002).
Understanding and using : english grammar ed.3 with answer key (Sastra Inggris).
Netherland:
Prentice Hall.
Gaya MLA
Azar, Betty, Schrampfer.
"Understanding and using : english grammar ed.3 with answer key".
Sastra Inggris
Netherland:
Prentice Hall,
2002.
.