Why are NFL players wearing padding on helmets at training camp?
Seeking to reduce head contact, NFL mandates use of Guardian Cap helmet for early portion of training camp - ESPN
High school football teams go soft in the fight against brain injuries
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
More Guardian Caps, And '0' On The Field
NFL Guardian Caps: How Do They Work? – NBC 5 Dallas-Fort Worth
What's with padded helmet caps teams are wearing
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
NFL hopes to reduce head injuries with helmet experiment – The Morning Call
No cap: Guardian covers are out, but one Steelers lineman plans to keep wearing it
What are Guardian Caps and how are they helping football teams?
Safety first: Lopers to wear padded caps in practice to prevent concussions
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
NFL training camps: Guardian Cap players are wearing over helmets, why