Guardian Cap Debuts at Training Camps League-wide
Coverage of the NFL in Guardian Caps
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk
NFL Releases Concussion Data After Use of 'Guardian Caps' During Offseason - Sports Illustrated
NFL reports reduction in concussions among players who wore Guardian Caps in preseason - The Athletic
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
What are Guardian Caps? NFL's latest padded helmets for added safety
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Guardian Partners With AYF - American Youth Football
AYF Archives - Guardian Sports
Coverage of the NFL in Guardian Caps
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk