NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Guardian cap' to prevent head injuries mandated for practices, CFL says
Guardian Cap Use a Concern for Watt, Saleh Early in Training Camp - Sports Illustrated
New Football Helmet Covers Improve Safety
Reduces impact up to 33% One size fits all Insulates in hot & cold weather
Guardian Protective Helmet Cover
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
How a soft-shell helmet is limiting the risk of concussions at Rutgers football camp
Guardian Caps Guardian Sports
Guardian cap' to prevent head injuries mandated for practices, CFL says
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN