National Football League Foundation - Wikipedia
Study: Heads Up program isn't helping limit youth football concussions
Can't concuss Orange County football, by Henry J. Medina
Football's CTE problem is real—divulging the NFL's dismissal of the disease and downplaying of concussion issues, by Michael Dong
Study shows positive results for Heads Up Football youth program
Opinion The Kids Who Still Need Football - The New York Times
NFL report: concussions dropped 50 PERCENT when players wore new 'Guardian Caps' over the summer
Concussion in the NFL: Study Shows Significant Detrimental Effects in the Short Term – Consult QD
Popular NFL-backed Heads Up tackling method questioned by former players - ESPN