I've since found two more versions of Steve Martin's cards.

1.http://www.betterlist.com/card.jpg

and the back cover of Carrie Fischer's book titled "Postcards from the edge" also has a card on it with a blurb about Steve's review of her book. Something about Moby Dick being fat and boring in comparison. I shall see if I can scan it. Maybe someone can find it on the web...