NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
Guardian Caps Exceed NFL's Expectations - Guardian Sports
It's not OK': NFL concussions rose 16% in 2017 amid CTE fears, Concussion in sport
Football Guardian Cap draws mixed reviews from players, experts for safety effectiveness - The Daily Tar Heel
NFL Releases Concussion Data After Use of 'Guardian Caps' During Offseason - Sports Illustrated
Sam Shields: Super Bowl champion regrets playing in NFL; says his head is 'all mushed together' with concussions
Off and Running - High School Season in Full Swing by Let's Play Hockey - Issuu
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Explaining the NFL's latest concussion controversy and policy change : NPR
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
NFL hopes to reduce head injuries with helmet experiment
NFL: Concussions dropped by more than 50% among players who wore Guardian Caps during summer
NFL report: concussions dropped 50 PERCENT when players wore new 'Guardian Caps' over the summer