Are concussions going down in football? Experts say we're starting to see some progress
Calvin Johnson: Playing through concussions is part of NFL life
Concussion Researchers Consulted With NFL Players' Lawyers
NFL concussions strategy for Super Bowl 52 includes a change
Concussion Treatment, Neurologists
Before 'Concussion': Mike Webster's Shattered Life
The link between head injuries and CTE in football, explained - Vox
What is C.T.E.? - The New York Times
Explaining the NFL's latest concussion controversy and policy change : NPR