Former NFL player accused of killing six people was suffering from severe CTE, Concussion in sport
September 2013 – The Concussion Blog
Head case: Batting helmet's development began in Pittsburgh
Guardian Caps: What are they and why are NFL players wearing them? - Sactown Sports
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Cardinals remove Kyler Murray's film study addendum from $230.5m deal, Arizona Cardinals
Guardian Cap Debuts at Training Camps League-wide
Cleveland's hangover cure? An Indians World Series title, Cleveland Guardians
Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77