NFL CMO Dr. Sills on Guardian Caps Mandate >> Guardian Sports
NFL's handling of concussions questioned after Tua's injury
Raiders, other NFL teams wear Guardian Caps for head safety, Raiders News
NFL Presents: League-wide Guardian Cap Use to Reduce Head Impacts
Coverage of the NFL in Guardian Caps
Dr. Allen Sills talks about the NFL's phased approach in returning to facilities
Coverage of the NFL in Guardian Caps
Guardian Caps — Do They Work? - The Indiana High School Football Forum - The Gridiron Digest
Seeking to reduce head contact, NFL mandates use of Guardian Cap helmet for early portion of training camp - ESPN