NFL rule changes for 2021; jersey number expansion
NFL owners pass rule expanding eligible jersey numbers for certain positions
How is a player's jersey number decided in football? - Quora
A numbers game: 2 officials change uniform numbers – Football Zebras
2021 N.F.L. Rule Changes: A Viewer's Guide - The New York Times
Breaking down the NFL's 6 new rules for 2021 season - Pride Of Detroit
NFL jersey number restrictions could change for running backs, receivers, tight ends, linebackers, defensive backs
NFL stars excited by zero jersey number rule change
Tom Brady slams NFL's jersey number rule: 'Dumb'