NFL's top doctor does not expect Guardian Caps to be worn in games - NBC Sports
Players, coaches react to mandatory use of Guardian Caps
NFL hopes to reduce head injuries with helmet experiment
NFL hopes to reduce head injuries with helmet experiment
What are Guardian Caps? Shadow Hills football using new device to reduce head injuries
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
The Coat of Arms Added Protection or False Security: Football Tests New Guardian Caps to Prevent Concussions
Guardian Cap Use a Concern for Watt, Saleh Early in Training Camp - Sports Illustrated
NFL introduces Guardian Caps across league to limit number of brain injuries in preseason
If a player wanted to wear a Guardian Cap during a game, the league would prohibit it - NBC Sports
UGA football outfits players in Guardian Caps to try to reduce impacts.