Gaya APA

Erkelens, J., Pudjamarsa, A. (2009). Understanding and Using English Grammar : fourth edition with answer key (fourth.ed). Jena :: Pearson longman.

Gaya MLA

Erkelens, J., Pudjamarsa, Astu. "Understanding and Using English Grammar : fourth edition with answer key". fourth.ed Jena :: Pearson longman, 2009. Text.