APA (7th ed.) Citation

Dr. Seuss. (2008). Horton hears a who! HarperCollins childrens books.

Chicago Style (17th ed.) Citation

Dr. Seuss. Horton Hears a Who! UK: HarperCollins childrens books, 2008.

MLA (9th ed.) Citation

Dr. Seuss. Horton Hears a Who! HarperCollins childrens books, 2008.

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