College football 2021: Return to normal wrapped in change
How empty stadiums contributed to the fight against Covid-19
NFL Health and Safety Fact Sheet
Friendly skies? Study charts Covid-19 odds for plane flights, MIT News
NFL vs. covid MIT Technology Review
Why the NFL can play football, and colleges can't - The Boston Globe
NFL and NFL Players Association drop all COVID protocols for 2022 season : Coronavirus Updates : NPR
Tracking the Spread Harvard Medical School
NFL is still committed to playoffs despite more Covid-19 outbreaks
Some NFL teams impose vaccine rules for fans, but Bills and Erie County stand pat