Guardian Caps debut at NFL training camps around the league
Guardian cap' to prevent head injuries mandated for practices, CFL says
NFL players experiment with 'Guardian Caps' to protect heads
If a player wanted to wear a Guardian Cap during a game, the league would prohibit it - NBC Sports
Guardian Caps Debut During NFL Minicamps
Saints adjusting to use of Guardian Caps in training camp - Daily Leader
Puffy Guardian Caps Could Reduce NFL Player Concussions
EXPLAINER: NFL using helmet caps for player safety, research
Concussions Dropped More Than 50 Percent for Players Who Wore Guardian Caps, NFL Says, News, Scores, Highlights, Stats, and Rumors
Here's why some Patriots players are wearing caps over their helmets during training camp
NFL hopes to reduce head injuries with 'goofy' helmet experiment
Coverage of the NFL in Guardian Caps