APA

Herrera M., Pinkley D., . (2005). Backpack 4. London: Pearson Longman.

Chicago

Herrera Mario, Pinkley Diane, . 2005. Backpack 4. London: Pearson Longman.

Harvard

Herrera M., Pinkley D., . (2005). Backpack 4. London: Pearson Longman.

MLA

Herrera Mario, Pinkley Diane, . Backpack 4. London: Pearson Longman. 2005.