NFL players wear Guardian Caps to reduce head trauma during training camp
Padded helmet cover shows little protection for football players - Scope
Large Bubble Helmets Are Guardian Caps, NFL's New Safety Measure
NFL training camps: Guardian Cap players are wearing over helmets, why
As NFL mandates Guardian caps in practice, area high school football teams have been using them for years, Sports
NFL says positions wearing Guardian Caps saw 52% decrease in concussions
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Concussions: Can cap keep football players' heads in game? – Orange County Register
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Guardian Cap Debuts at NFL Training Camps League-wide
NFL Introduces Guardian Caps At First Week Of Training Camp - The Sports Credential