Gaya APA

Greenwell, J., Lawrence, S. (2008). All of Us Student Book Level 6 Teacher's Material . Singapura: Mc Graw-Hill.

Gaya MLA

Greenwell, Jeanette., Lawrence, Stephen. "All of Us Student Book Level 6 Teacher's Material". Singapura: Mc Graw-Hill, 2008. Text.