Football helmet - Wikipedia
Players, coaches react to mandatory use of Guardian Caps
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
NFL hopes to reduce head injuries with helmet experiment
Camp Report: Falcons VP of player personnel Kyle Smith talks 'churning the roster'
September 2013 – The Concussion Blog
NFL commissioner Roger Goodell believes football will become safer
Jason Kelce puts bubblewrap on his helmet, mocking the NFL's dumb new Guardian Cap rules in training camp
Eagles players on Guardian Caps: 'We look a little goofy,' but all for safety
Get A Load Of These Big Dumb Helmet Helmets
NFL Guardian Caps: How Do They Work? – NBC 5 Dallas-Fort Worth