NFL: Concussions dropped by more than 50% among players who wore Guardian Caps during summer
Playing with a pillow on your head': Buffalo Bills embrace new helmet covers
What is the Q Collar, the device NFL players are wearing around their necks
NFL hopes to reduce head injuries with helmet experiment
NFL players wear Guardian Caps to reduce head trauma during training camp
NFL concussions plummet during preseason, rise in regular season
Guardian Caps data show more than 50% concussion drop among groups who wore them - Newsday
New devices, practice habits aim to curb concussions in high school football
Football helmet - Wikipedia
Coverage of the NFL in Guardian Caps
Cowboys wearing soft-shell helmets in practice as part of NFL mandate