Question: What is the publishing year of this children's book written and illustrated by Dr. Seuss, in which the featured characted was also part of a book "Horton Hatches the Egg"?
Sentence (from "Horton the Elephant"): Horton the Elephant is a fictional character from the 1940 book "Horton Hatches the Egg" and 1954 book "Horton Hears a Who!
Relevant evidence: Yes