Simplify the following text for a Grade 4 native English-speaking person.
Original: Though most were published under his well-known pseudonym , Dr. Seuss , he also authored over a dozen books as Theo LeSieg and one as Rosetta Stone .
Simplified: Though most of them were published as Dr. Seuss , he also wrote 13 books as Theo . LeSieg and one as Rosetta Stone ( a pun on the Rosetta Stone ) .