Can I Wear a Hat to Play Football?
NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games
Guardian Cap Debuts at Training Camps League-wide
Can Soccer Players Wear Hats? - Soccer Knowledge Hub
Football's top 10 hat wearers - Wales Online
Can footballers wear a baseball cap during a match? - Premier Football UK
The story behind those soft-shell puffy Guardian Caps players have been wearing
NFL players experimenting with 'Guardian Caps' to prevent head injuries
Guardian Caps', NFL's Most Recent Attempt At Preventing Head Injuries
Giant hats: How NFL player Brian Robinson sparked the most genius marketing stunt
Guardian Caps may one day be worn by players in NFL games, league executive says
This Is Why NFL Players Are Wearing Tie-Dye Hats on Game Day
Players, coaches react to mandatory use of Guardian Caps
NFL training camps: Guardian Cap players are wearing over helmets, why