Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
NFL hopes to reduce head injuries with helmet experiment – The Morning Call
What are Guardian Caps, and why are some NFL players wearing them during training camp?
Guardian Cap Debuts at Training Camps League-wide
NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games, National
NFL expands rule against misuse of helmet; Guardian Caps required in regular season, postseason
The 2022 Uni Watch NFL Season Preview - by Paul Lukas
NFL concussions Guardian Cap - TSN.ca
Guardian Cap Debuts at Training Camps League-wide
FOOTBALL: NFL following Sequim's lead with protective caps
Our sport can be safe and exciting': NFL points the way for dealing with concussion, NFL