Guardian Caps: Why some NFL players are wearing them in training camps
Helmet safety: Inside the complicated equipment industry - Sports Illustrated
The Extra Yard: The Ins and Outs of an American Football Helmet - Stories
Find out how modern football helmets attempt to limit brain injuries
3 Ingenious innovations from the NFL's Helmet Challenge
NFL Player Safety: The Case for Banning Helmets and Why It Could Make American Football Safer, News, Scores, Highlights, Stats, and Rumors
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Varsity Football Helmet Ratings
Beyond the Helmet: Protecting the Brain of Your Athlete
Football helmets are creating more problems than they solve