The impact of 'Guardian Caps' on player safety
NFL Executive VP: League Saw 52 Percent Decrease In Concussions At Positions Wearing Guardian Caps - Steelers Depot
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
NFL health and safety officials recommend expanded use of Guardian Caps - NBC Sports
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
NFL introduces Guardian Caps across league to limit number of brain injuries in preseason
EXPLAINER: NFL using helmet caps for player safety, research - The San Diego Union-Tribune
More Guardian Caps, And '0' On The Field
Large Bubble Helmets Are Guardian Caps, NFL's New Safety Measure
EXPLAINER: NFL using helmet caps for player safety, research