Ban on helmet covers sparks controversy
Football helmet design can lower concussion risk, study finds
Helmets don't eliminate concussions. It's time for the NFL to ditch them, NFL
Guardian Cap debuts during minicamps in effort to reduce avoidable head contact
NFL helmet manufacturers hope to reduce concussions, save game - Washington Times
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
Retired NFL Player Says It's Easy to Cheat the Concussion Protocol
Football helmet with liquid padding may prevent concussions
Limiting contact in practice may be one of the best ways to reduce head injuries in youth football, study finds
NFL, Players Union Agree to Change Concussion Protocol - The New York Times