Official Site of the National Football League
Odd & original football rules that are no longer used - Dawgs By Nature
What is American Football?
2023 NFL Record and Fact Book
History and Rules of American Football - GRIN
American football - Wikipedia
Gridiron football - Wikipedia
American football, Definition, History, Leagues, Rules, & Facts
American Football League (AFL), History, Joe Namath, & Teams
American football - Wikipedia
History and Rules of American Football - GRIN
The NFL's Racist 'Race Norming' Is an Afterlife of Slavery - Scientific American