NFL introduces Guardian Caps across league to limit number of brain injuries in preseason
NFL hopes to reduce head injuries with helmet experiment
Guardian cap' to prevent head injuries mandated for practices, CFL says
Steelers debut new, safer helmets for off-season training
GUARDIAN CAP DEBUTS AT TRAINING CAMPS LEAGUE-WIDE
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Guardian Cap: What are and why the NFL asks this safety measure in helmets
Truth About Guardian Caps
The Coat of Arms Added Protection or False Security: Football Tests New Guardian Caps to Prevent Concussions
NFL report: concussions dropped 50 PERCENT when players wore new 'Guardian Caps' over the summer
First QB helmet designed to help reduce concussions approved by NFL, NFLPA
Why are some Titans players wearing Guardian Caps during training camp?, Titans
NFL players experiment with 'Guardian Caps' to protect heads - The San Diego Union-Tribune