NFL number changes: list of players who have switched jersey numbers
List of NCAA football retired numbers - Wikipedia
BU Finds CTE in Nearly 92 Percent of Ex-NFL Players Studied, The Brink
List of NCAA football retired numbers - Wikipedia
List of NCAA football retired numbers - Wikipedia
What are some “unofficially” retired numbers that are not reissued? : r/nfl
List of National Football League retired numbers - Wikipedia
Why is Archie Manning's Saints jersey the only one unofficially retired?
Luke Kuechly reminds us how hard it is for NFL players to retire
List of NCAA football retired numbers - Wikipedia