Eagles players on Guardian Caps: 'We look a little goofy,' but all for safety
NFL players experiment with 'Guardian Caps' to protect heads
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
[Smith] NFL says positions wearing Guardian Caps saw 52% decrease in concussions : r/nfl
NFL Health and Safety Fact Sheet
FOOTBALL: NFL following Sequim's lead with protective caps
Ravens Embrace the Funny-Looking Guardian Helmets - Sports Illustrated Baltimore Ravens News, Analysis and More
NFL hopes to reduce head injuries with helmet experiment
Guardian cap' to prevent head injuries mandated for practices, CFL says
Ban on helmet covers sparks controversy
Guardian Cap Debuts at Training Camps League-wide
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Concussions: Can cap keep football players' heads in game? – Orange County Register
Guardian Caps Debut at Training Camps Across the NFL