Guardian Caps: Why some NFL players are wearing them in training camps
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
Coverage of the NFL in Guardian Caps
Coverage of the NFL in Guardian Caps
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