Tennessee football: UT Vols use Guardian helmet covers
NFL hopes to reduce head injuries with helmet experiment - The San Diego Union-Tribune
Here's why some Patriots players are wearing caps over their helmets during training camp
NFL introduces Guardian Caps across league to limit number of brain injuries in preseason
NFL players experiment with 'Guardian Caps' to protect heads
Bellmore-Merrick athletics debuts new guardian caps, Herald Community Newspapers
Guardian Caps: Why some NFL players are wearing them in training camps
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Browns wearing Guardian Caps during training camp