Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
Guardian Caps', NFL's Most Recent Attempt At Preventing Head Injuries
Buffalo Bills Accustomed to NFL Mandated Guardian Caps: Controversial Change - Sports Illustrated Buffalo Bills News, Analysis and More
NFL's use of Guardian padded helmet caps in camp draws support and skepticism - The Athletic
Seeking to reduce head contact, NFL mandates use of Guardian Cap helmet for early portion of training camp - ESPN
Robert Saleh dislikes the new Guardian Caps: And he has a point
CFL players adjust to protective helmet caps
Guardian Caps: What are they and why are NFL players wearing them? - Sactown Sports
Have you seen the strange helmets Cowboys players are wearing in camp? Here's the story
Guardian Cap Debuts at Training Camps League-wide