Guardian Caps Guardian Sports
NFL takes first-ever step to ban some helmets after testing - The San Diego Union-Tribune
NFL helmet safety testing results: Vicis ranks first again for its high-tech head protector – GeekWire
NFL Testing Safer Helmets
With concussions at forefront of minds, helmet designs more important
NFL testing 3D printed helmets from Carbon, Peyton Manning excited
Everything you need to know about the NFL's helmet guidelines and restrictions - Canal Street Chronicles
NFL hopes to reduce head injuries with 'goofy' helmet experiment
New Smart Helmet Could Spot Concussions in Real Time
The NFL's Helmet Tests Are Brainless