Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk
NFL training camps: Guardian Cap players are wearing over helmets, why
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
NFL hopes to reduce head injuries with helmet experiment, FOX 4 Kansas City WDAF-TV
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Why are NFL players wearing padding on helmets at training camp?
NFL Presents: League-wide Guardian Cap Use to Reduce Head Impacts
NFL offseason priorities for 2023: Possible rules changes, safety reforms - ESPN
NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games
Guardian Cap Debuts at NFL Training Camps League-wide
NFL expands rule against misuse of helmet; Guardian Caps required in regular season, postseason
2011 Army Football Media Guide by Army West Point Athletics - Issuu
4-29-23 Emerald Media Group - Gameday by Emerald Media Group - Issuu
Guardian Caps NFL: What player positions are required to wear them?