Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Why are players wearing padded helmets at NFL training camps?
NFL: Concussions dropped by more than 50% among players who wore Guardian Caps during summer
NFL players wear Guardian Caps to reduce head trauma during training camp
Guardian Cap Use a Concern for Watt, Saleh Early in Training Camp - Sports Illustrated
Guardian Caps Guardian Sports
Arizona Cardinals defensive end J.J. Watt not fan of the new league-mandated Guardian Caps on helmets
Coverage of the NFL in Guardian Caps
What is a Guardian Cap? Meet the NFL's newest safety measure
Guardian Caps Guardian Sports