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 "Dr. Seuss bibliography"): In the years following his death in 1991, several additional books based on his sketches and notes were published, including "Hooray for Diffendoofer Day!
Relevant evidence: No