Funky-Looking Guardian Caps Rejected by NFL for Regulation Play, OK'd for Practice - Core77
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
Analysis: Why Seahawks didn't make moves at NFL trade deadline
Richard Sherman explains post-game rant in Sports Illustrated column: 'It was just a small part of the person I am'
Jonathan Allen clearly isn't a fan of NFL's mandated safety helmets
NFL says positions wearing Guardian Caps saw 52% decrease in concussions - NBC Sports
Guardian Caps: NFL's hotly debated new safety measure here to stay?
Bloomberg Businessweek - FTP Directory Listing
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp