NFL's use of Guardian padded helmet caps in camp draws support and skepticism - BVM Sports
What are those helmet pads Chicago Bears offensive linemen have been wearing at practices?
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
In fall camp, Montana State using Guardian Caps for safety, preservation of game
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
Guardian Football Cover Cap XT
NFL hopes to reduce head injuries with helmet experiment
Raiders, other NFL teams wear Guardian Caps for head safety, Raiders News
Why are NFL players wearing padding on helmets at training camp?
Jaguars Add Davis, MacCracken, Hughes to Personnel Staff
NFL players wear Guardian Caps to reduce head trauma during training camp
Football Guardian Cap draws mixed reviews from players, experts for safety effectiveness - The Daily Tar Heel