NFL owners pass rule expanding eligible jersey numbers for certain positions
NFL approves rule change on jersey number, nixes overtime shifts
New NFL jersey numbers, explained: What to know about league's rule change for 2021
NFL jersey number rules, explained: Why these players changed numbers for 2021 season
NFL CBA approved - What players get in new deal, how expanded playoffs and schedule will work - ESPN
NFL Rules Players Must Follow
NFL rule changes for 2021; jersey number expansion
Single-Digit Jerseys Should Be the NFL's Most Exclusive Club - The Ringer
The NFL Jersey Number Rule Explained - HowTheyPlay