Large Bubble Helmets Are Guardian Caps, NFL's New Safety Measure
High school helmets: Much changed, but how much they protect against concussions is questionable, experts say, Local News, Selma / Kingsburg
A concussion-proof helmet? It doesn't exist today and may be an impossible dream
Flexible NFL helmet aims to reduce head injuries
This Helmet Will Save Football. Actually, Probably Not. - The New York Times
New helmet design can deal with sports' twists and turns
Concussion in Kids Midwest Orthopedic Specialty Hospital
Revolutionary new ZERO1 football helmet may help NFL players reduce concussions
Football helmets don't prevent concussions. What can?
Find out how modern football helmets attempt to limit brain injuries
NFL: Concussions dropped by more than 50% among players who wore Guardian Caps during summer
NFL players don Guardian Caps, designed to protect from concussion
New high-tech helmets may protect American football players from debilitating concussions