Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
EXPLAINER: NFL using helmet caps for player safety, research - The San Diego Union-Tribune
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Steelers debut new, safer helmets for off-season training
What are the padded helmets players are wearing at NFL training camps?
What are Guardian Caps and how are they helping football teams?
Bombers set to don Guardian Caps” on helmets at training camp
As NFL mandates Guardian caps in practice, area high school football teams have been using them for years, Sports
The impact of 'Guardian Caps' on player safety
It's time the NFL made Guardian Caps mandatory