What are NFL players wearing on their helmets at training camp and how do they work? - The Mirror US
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Giants react to NFL's new 'Guardian Caps' at training camps - Big Blue View
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries : r/nfl
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Eagles players on Guardian Caps: 'We look a little goofy,' but all for safety
If a player wanted to wear a Guardian Cap during a game, the league would prohibit it - NBC Sports
Guardian Caps: The new helmets worn by several NFL teams
Guardian Caps, a soft-shell helmet cover, among CFL's new player-safety initiatives
What are Guardian Caps? NFL's latest padded helmets for added safety
Guardian Caps: Why some NFL players are wearing them in training camps