The potential solution to serious head injuries in football is counter-intuitive - Hogs Haven
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
The NFL Has Introduced 'Guardian Caps' to Reduce Concussions, and Made Them Mandatory. But Only for Some Positions. And Only Through the 2nd Preseason Game.
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Coverage of the NFL in Guardian Caps
Colin Kaepernick - Wikipedia
Why are NFL players wearing padding on helmets at training camp?
NFL players wear Guardian Caps to reduce head trauma during training camp
NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
NFL expands rule against misuse of helmet; Guardian Caps required in regular season, postseason
Guardian Cap Debuts at Training Camps League-wide