Some CFL players are wearing foam covers on helmets
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Guardian Caps: The new helmets worn by several NFL teams
MTSU reduces concussion risk with padded helmet covers
Xaverian High in Mass. introduces Guardian Caps for football players
NFL hopes to reduce head injuries with helmet experiment
Chicago Bears: Why players are wearing padded helmets
Bellmore-Merrick athletics debuts new guardian caps, Herald Community Newspapers
Why are NFL players wearing padding on helmets at training camp?
NFL players wear Guardian Caps to reduce head trauma during training camp
Virginia Tech Helmet Lab tests SAFR Helmet Covers, orders 110 for the VA Tech football team – SAFR Sports