NFL Testing Safer Helmets
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
NFL players experiment with 'Guardian Caps' to protect heads
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
The Coat of Arms Added Protection or False Security: Football Tests New Guardian Caps to Prevent Concussions
Helmet Innovation: More and Better Choices, Fewer Concussions
The link between head injuries and CTE in football, explained - Vox
Explanation: NFL using helmet caps for player safety, research
NFL hopes to reduce head injuries with helmet experiment
The Future of NFL Defenses Lies in a Lime-Green Dot - The Ringer
In NFL, deeply flawed concussion research and ties to Big Tobacco