Football helmet - Wikipedia
Sapakoff: If Guardian Caps help football brains, use them in games
Guardian Caps - Are the soft-shelled football helmet covers
Guardian Caps Exceed NFL's Expectations - Guardian Sports
NFL Health and Safety Fact Sheet
NFL players wear Guardian Caps to reduce head trauma during
NFL: Concussions dropped by more than 50% among players who wore
NFL Say Concussions Have Dropped by 50 Percent Since Introducing
Concussions in NFL are up again after two seasons of declines
Puffy Guardian Caps Could Reduce NFL Player Concussions
NFL concussions Guardian Cap - TSN.ca
football Archives - Guardian Sports