NFL says Guardian Caps reduced concussions by over 50%
A closer look at the rule changes the NFL is debating - The Washington Post
Large Bubble Helmets Are Guardian Caps, NFL's New Safety Measure
Why Utah players wore Guardian Caps during camp - Deseret News
Coverage of the NFL in Guardian Caps
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
What are Guardian Caps? Shadow Hills football using new device to reduce head injuries
NFL players experimenting with 'Guardian Caps' to prevent head injuries
Coverage of the NFL in Guardian Caps