National Football League

Official 2014 National Football League record & fact book

2008 Official playing rules of the National Football League

The official 2004 National Football League record & fact book

Official 2012 National Football League Record Fact Book

Official 2009 National Footbal League Record Fact Book

Constitution and Bylaws of the National Football League

2010 Official Playing Rules Of The National Football League

Official National Football League record & fact book

NFL Report '77