APA-referens (7:e uppl.)

Willems, M. (2011). Happy Pig Day! Hyperion Books for Children.

Chicago-referens (17:e uppl.)

Willems, Mo. Happy Pig Day! New York: Hyperion Books for Children, 2011.

MLA-referens (8:e uppl.)

Willems, Mo. Happy Pig Day! Hyperion Books for Children, 2011.