APA Style

Stilton, G., Keys, L. (2004). Geronimo Stilton Merry Christmas, Geronimo! . New York, USA: Scholastic Inc.

MLA Style

Stilton, Geronimo., Keys, Larry. "Geronimo Stilton Merry Christmas, Geronimo!". New York, USA: Scholastic Inc, 2004. Text.