Bernice E. Cullinan, Diane Goetz Person: The Continuum Encyclopedia of Children’s Literature. A&C Black, 2005, ISBN 978-0-8264-1778-7, S.147 (google.de).
Carol M. Butzow, John W. Butzow: Science Through Children’s Literature: An Integrated Approach. Libraries Unlimited, 2000, ISBN 978-1-56308-651-9, S.57 (google.de).