Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
New Football Helmet Covers Improve Safety
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Some CFL players are wearing foam covers on helmets
Eagles players on Guardian Caps: 'We look a little goofy,' but all for safety
EXPLAINER: NFL using helmet caps for player safety, research - The San Diego Union-Tribune
Guardian Caps, a soft-shell helmet cover, among CFL's new player-safety initiatives
Guardian Caps', NFL's Most Recent Attempt At Preventing Head Injuries
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Guardian Caps: What Are They & How Do They Work?
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post