By DAN GELSTON
AP Sports Writer
The number of movies, documentaries and other entertainment vehicles made about Muhammad Ali would make it seem that there’s not much left to offer. But documentary filmmaker Ken Burns knew there were more layers to reveal in Ali’s rise from his Louisville, Kentucky, roots into the source of Black pride who captivated America with his boxing braggadocio and his contentious decision to refuse to fight in Vietnam. Burns began work on the Ali film nearly seven years ago and says Ali is “compelling,” “complicated” and “a transcendent American character.” The four-part, eight-hour series airs Sept. 19-22 on PBS.