Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
Could Guardian Caps be used in games? : r/nfl
Smith] NFL says positions wearing Guardian Caps saw 52% decrease in concussions : r/nfl
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk
NFL players don Guardian Caps, designed to protect from concussion
Eagles players on Guardian Caps: 'We look a little goofy,' but all for safety
NFL Mandated Guardian Caps: Controversial Change - Sports Illustrated Seattle Seahawks News, Analysis and More
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
Steelers debut new, safer helmets for off-season training
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk