APA (7th ed.) Citation

Seuss, D. (1976). Horton hears a Who! / by Dr Seuss. Collins.

Chicago Style (17th ed.) Citation

Seuss, Dr. Horton Hears a Who! / by Dr Seuss. London: Collins, 1976.

MLA (9th ed.) Citation

Seuss, Dr. Horton Hears a Who! / by Dr Seuss. Collins, 1976.

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