The original series was written by the team of Hans Augusto Rey and Margret Rey. The Jewish couple fled Paris in June 1940, on self made bicycles, carrying the Curious George manuscript with them. At first, only H. A. Rey was credited for the work in order to distinguish the Reys' books from the large number of children's books written by female authors. The first seven books were illustrated by H. A. Rey. Later, Alan Shalleck was credited for the illustrations and Hans Rey and Margret Rey for the writing. The Reys produced many other children's books, but the Curious George series was the most popular. Each book has been in continuous print since it was first published.