Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
Giants react to NFL's new 'Guardian Caps' at training camps - Big Blue View
Guardian Caps: Why some NFL players are wearing them in training camps
If a player wanted to wear a Guardian Cap during a game, the league would prohibit it - NBC Sports
Guardian Caps: What Are They & How Do They Work?
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
NFL hopes to reduce head injuries with helmet experiment - Wilmington News Journal
High school football teams go soft in the fight against brain injuries
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries : r/nfl
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
What is a Guardian Cap? Meet the NFL's newest safety measure