Bennet Omalu, Concussions, and the NFL: How One Doctor Changed Football Forever
NFL says positions wearing Guardian Caps saw 52% decrease in concussions - NBC Sports
Armor on the Field: The NFL's Headlong Race to Build the Unbreakable Linebacker
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Helmet manufacturers work on safer youth equipment
What Pros Wear: Top 5 Helmets Rated by the NFL & NFLPA - What Pros Wear
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
Bellmore-Merrick athletics debuts new guardian caps, Herald Community Newspapers
The link between head injuries and CTE in football, explained - Vox