Dallas Cowboys - Wikipedia
NFL says Guardian Caps reduced concussions by over 50%
Concussions in NFL are up again after two seasons of declines - The Washington Post
NFL Executive VP: League Saw 52 Percent Decrease In Concussions At Positions Wearing Guardian Caps - Steelers Depot
Limiting contact in practice may be one of the best ways to reduce head injuries in youth football, study finds
NFL says positions wearing Guardian Caps saw 52% decrease in concussions - NBC Sports
Guardian Cap Results: “Exceeded Our Expectations”
NFL hopes to reduce head injuries with helmet experiment –
Georgia State trying out safety device on helmets