Padded helmet cover shows little protection for football players - Scope
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
What are the padded helmets players are wearing at NFL training camps?
Xaverian High in Mass. introduces Guardian Caps for football players
EXPLAINER: NFL using helmet caps for player safety, research
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games
NFL says positions wearing Guardian Caps saw 52% decrease in concussions
Guardian Caps: The new helmets worn by several NFL teams
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
More padding the issue of concussions and better helmets