Chris Borland retires from 49ers after one year due to fears over head trauma, NFL
Carl Nassib retires: Ex-Raider was first openly gay NFL player, Raiders News
Football 'literally killed' 24-year-old Zac Easter of Iowa. His family vows to make the sport safer.
San Francisco 49ers' Chris Borland Retires at 24 Over Concussion and Brain Trauma Worries - The Atlantic
Jets cornerback D.J. Reed will sit out against the Broncos with a concussion
Concussion Concern: LB Retires After One NFL Season
Chris Borland retires from NFL at just 24 years old, makes his own sense of head injuries – New York Daily News
Lawsuit Alleges NFL's Concussion Settlement Discriminates Against Black Players - WSJ
NFL Concussions: The 2013-14 Season In Review
UT Southwestern Medical Center begins two-year study on brain health
Chris Borland's early retirement shifts focus of head injuries in NFL - Los Angeles Times