Guardian Cap: What are and why the NFL asks this safety measure in helmets
This Helmet Will Save Football. Actually, Probably Not. - The New York Times
Hockey Helmets: A Way to Make Them Safer?
History of The Football Helmet - Atavus
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
SAFR Helmet Covers – SAFR Sports
Everything you need to know about the NFL's helmet guidelines and restrictions - Canal Street Chronicles
Do helmets actually make football safer? SiOWfa16: Science in Our World: Certainty and Controversy
Varsity Football Helmet Ratings
The Extra Yard: The Ins and Outs of an American Football Helmet - Stories
New Smart Helmet Could Spot Concussions in Real Time
The Q-Collar is the only FDA-cleared sports equipment that helps protect athletes' brains from the effects of repetitive sub-concussive head impacts. BUY NOW!.
Soft Protective Headgear Buy Soft Shell Helmets & Protective Padded Equipment Online - GameBreaker
NFL safety: How VICIS' position-specific helmets have become all the rage - The Athletic