NFL Health and Safety Fact Sheet
Guardian Cap: What are and why the NFL asks this safety measure in helmets
Guardian cap' to prevent head injuries mandated for practices, CFL says
Guardian Caps: NFL requires use of helmet cover at training camps to reduce head injuries
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
Guardian cap' to prevent head injuries mandated for practices, CFL says
Park High School football blazes safety trail with Guardian Caps
Guardian Caps Guardian Sports
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
NFL with no quarterbacks? The league's Covid-19 problems are just starting, Denver Broncos
College football safety gets shaped by research, including possible head-hit counts