APA (7th ed.) Citation

Willems, M. (2007). My friend is sad. Hyperion Books for Children.

Chicago Style (17th ed.) Citation

Willems, Mo. My Friend Is Sad. New York: Hyperion Books for Children, 2007.

MLA (8th ed.) Citation

Willems, Mo. My Friend Is Sad. Hyperion Books for Children, 2007.

Warning: These citations may not always be 100% accurate.