Peace Puzzler

Here is a Peace puzzler. It has to do with the book itself, not its contents, so there may actually be an answer to this question. Who drew the cover art? The back of the Orb edition says: Cover art by Gahan Wilson But the copyright page says: Cover art by Tony Roberts Which one was it? Is Tony Roberts really Gahan Wilson? Then who acted in all those Woody Allen movies? I'm puzzled! William Ansley