 His book "The Girl Who Loved Wild Horses" won the Caldecott Medal in 1979.Lakota scholar Elizabeth Cook-Lynn (Cook-Lynn, 1998) and Lakota librarian Doris Seale find his retellings inaccurate.Displeasure in them led the American Indian Library Association to ask the American Library Association to withdraw "Native American Month" posters and bookmarks with his art on them in 2007.