Seeking to reduce head contact, NFL mandates use of Guardian Cap helmet for early portion of training camp - ESPN
NFL players don Guardian Caps, designed to protect from concussion
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
NFL players wear Guardian Caps to reduce head trauma during training camp
NFL training camps: Guardian Cap players are wearing over helmets, why
Raiders, other NFL teams wear Guardian Caps for head safety, Raiders News
NFL training camps: Guardian Cap players are wearing over helmets, why
Why are NFL players wearing padding on helmets at training camp?
It's time the NFL made Guardian Caps mandatory
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN