NFL reports reduction in concussions among players who wore Guardian Caps in preseason - The Athletic
How football helmets fail to protect against some of the most dangerous hits in the game - The Verge
What Pros Wear: Top 5 Helmets Rated by the NFL & NFLPA - What Pros Wear
NFL hopes to reduce head injuries with helmet experiment - Seattle Sports
Guardian Caps: Why some NFL players are wearing them in training camps
NFL training camps: Guardian Cap players are wearing over helmets, why
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Padded helmet cover shows little protection for football players - Scope
Large Bubble Helmets Are Guardian Caps, NFL's New Safety Measure
NFL players wear Guardian Caps to reduce head trauma during training camp
What is the NFL Guardian Cap? Will it do anything to reduce concussion? — Dr. Mark Heisig
GUARDIAN CAP DEBUTS AT TRAINING CAMPS LEAGUE-WIDE
NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games