Guardian Caps: What are they and why are NFL players wearing them? - Sactown Sports
Helmets don't eliminate concussions. It's time for the NFL to ditch them, NFL
Truth About Guardian Caps
Coverage of the NFL in Guardian Caps
If a player wanted to wear a Guardian Cap during a game, the league would prohibit it - NBC Sports
Giants react to NFL's new 'Guardian Caps' at training camps - Big Blue View
NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games
NFL players wear Guardian Caps to reduce head trauma during training camp
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
NFL training camps: Guardian Cap players are wearing over helmets, why
What are those funny-looking soft caps on NFL helmets during camp?, Sports
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
NFL players don Guardian Caps, designed to protect from concussion