Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk
Park High School football blazes safety trail with Guardian Caps
Could Guardian Caps be used during NFL games for player safety?, Pro Football Talk
Guardian Cap Debuts at Training Camps League-wide
SBJ Closing Bell: NFL makes ambitious direct-to-consumer move
What Pros Wear: Guardian Caps What are Those Helmet Covers Being Worn in Practice? - What Pros Wear
NFL players wear Guardian Caps to reduce head trauma during training camp
Arizona Cardinals defensive end J.J. Watt not fan of the new league-mandated Guardian Caps on helmets
Asked and Answered: Aug. 3
Guardian Cap Debuts at Training Camps League-wide
Seeking to reduce head contact, NFL mandates use of Guardian Cap helmet for early portion of training camp - ESPN
Kiski Area football adds Guardian Caps for extra level of safety during practice
CFL introduces mandatory extra helmet protection for multiple positions. As well as other new health & safety measures. : r/sports
NFL Health and Safety Fact Sheet