Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
September 2013 – The Concussion Blog
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
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
NFL hopes to reduce head injuries with helmet experiment
Why are NFL players wearing padding on helmets at training camp?
Best New Gear and Coolest Gadgets This Week, According to Men's Journal - Men's Journal
Shell game: Player safety looming concern as new season approaches, Local Sports