The Cat In the Hat's Learning Library Set of Four - There's No Place Like Space! - Oh, The Pets You Can Get!, - Oh Say Can You Say Di-no-saur? - Hop on Pop

Random House set of four hardcovers - copyrights 1991, two 1999 and one 2005 - Hop on Pop is an "I Can Read It All By Myself" and the rest are "The Cat in the Hat Learning Library" for Beginning Readers.