The NFL's official encyclopedic history of professional football: Bennett, Tom; Boss, David; Campbell, Jim; Siwoff, Seymour; Smith, Rick; Wiebusch: 9780025890107: : Books
The NFL: 100 Years of football - Los Angeles Times
Passing Through Time, a 1930s Rule Change Started the NFL on its Way to Wide Open Offense
10 Oldest Teams in the NFL
Super Bowl, History, Appearances, Results, & Facts
A Brief History of the Super Bowl - Ball State Daily
Official Site of the National Football League
Timeline of the National Football League - Wikipedia