The cat in the hat dictionary,
by the Cat himself and P. D. Eastman.

APA Citation

Seuss, D., Eastman, P. D. (Philip D.). (1964). The cat in the hat dictionary. [New York]: Beginner Books.

MLA Citation

Seuss, Dr, and P. D. (Philip D.) Eastman. The Cat In the Hat Dictionary. [New York]: Beginner Books, 1964.

Warning: These citations may not always be complete (especially for serials).