NFL players wear Guardian Caps to reduce head trauma during training camp
This Brain Doc Has a “Repulsive” Idea to Make Football Safer
New Football Helmet Could Save the Sport
Complaints begin regarding Guardian Caps, despite one important hidden benefit - NBC Sports
New Helmet Technology Aimed to Make Football and Other Sports Safer
How New Helmet Technology Will Make the NFL and NHL Safer, News, Scores, Highlights, Stats, and Rumors
Guardian Caps Guardian Sports
Guardian Cap Debuts at Training Camps League-wide
Antonio Brown's dispute with the NFL over a helmet, explained
From Head To Toe And More - Mississippi State
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
What are those caps football players are wearing?
Guardian Caps: Why some NFL players are wearing them in training camps
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post