NFL expands rule against misuse of helmet; Guardian Caps required in regular season, postseason
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
Puffy, spongy Guardian Caps could help curb NFL head injuries - The Washington Post
NFL expands rule against misuse of helmet; Guardian Caps required in regular season, postseason
NFL notebook: Ingram getting closer to return
Football helmet - Wikipedia
Page 34 – Business Law Today from ABA
Rethinking Turf From The Ground Up
Players, coaches react to mandatory use of Guardian Caps
Guardian Caps leave some NFL players and coaches with concerns: 'You feel like a bobblehead'
Guardian Cap Use a Concern for Watt, Saleh Early in Training Camp - Sports Illustrated