APA
Martin B., . (2007). Polar bear, polar bear, what do you hear?. London: Puffin Books.
Chicago
Martin Bill, . 2007. Polar bear, polar bear, what do you hear?. London: Puffin Books.
Harvard
Martin B., . (2007). Polar bear, polar bear, what do you hear?. London: Puffin Books.
MLA
Martin Bill, . Polar bear, polar bear, what do you hear?. London: Puffin Books. 2007.