A new book claims the NFL spent two decades trying to deny the long-term effects of concussions.  Two ESPN investigative reporters co-authored "League of Denial: The NFL, Concussions and the Battle for Truth."  Published excerpts by "ESPN The Magazine" and "Sports Illustrated" say the league used its influence to discredit concussion research and keep the public in the dark about what NFL executives really knew about the long-term damage of playing football.  The NFL settled a concussion lawsuit last month brought on by thousands of former players for 765-million-dollars.