ProCap Football Helmet Accessory
Helmets Preventing Concussion Seen Quashed by NFL-Riddell - Bloomberg
More Helmet News: Oversized Helmet? – The Concussion Blog
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Concussion List Tracker for NFL Players, plus NFL Concussion Protocol Policies
Once shunned by NFL, 'disruptive' helmet inventor believes his time has come
Coaches tackle playing safety at AFCA convention
The First Plastic Football Helmet Often Broke on Impact - The Atlantic
Bring back The ProCap – Concussions In The NFL
File:Mark Kelso's special helmet (3813492425).jpg - Wikipedia
NFL concussion protocol: What are the steps for return to play?
Pennsylvania businesses look to grow while helping protect against sports concussions
What's with padded helmet caps teams are wearing
The NFL and players union agreed to an updated concussion protocol : NPR