Gaya APA

Schoenberg.--, I, E, S, I, E. (2001). Focus on grammar an introductory course for reference and practice.-- . USA : Longman.

Gaya MLA

Schoenberg.--, Irene, E., Schoenberg., Irene, E.. "Focus on grammar an introductory course for reference and practice.--". USA : Longman, 2001. Buku.