NFL 101: Beginner's Guide on How the NFL Works
A Beginner's Guide to American Football
How do NFL overtime rules work in the Super Bowl? - The San Diego Union-Tribune
NFL practice squads, explained: How it works, rules, eligibility, more - Pats Pulpit
Football 101: Coverage Shells - The Phinsider
The N.F.L. Struggles to Tackle Its Latest Problem: Tackling - The New York Times
How it works: NFL Practice Squad rules, eligibility, salary, and more - Hogs Haven
A Beginner's Guide to American Football
How to Play American Football: 10 Steps (with Pictures) - wikiHow