Should the NFL be Afraid of Chris Borland?
Badgers who walked away from football after concussions
NFL: Early retirements over health fears may have ripple effect
Chris Borland retires from NFL at just 24 years old, makes his own sense of head injuries – New York Daily News
49ers among biggest hit by early retirements of Borland, Anthony Davis, Willis
Chris Owusu: Big Decision Coming Following 5th Concussion - Gang Green Nation
Chris Borland's retirement: Is an NFL player's brain really more important than his feet?
Chris Borland retires: NFL must improve player safety - Sports Illustrated
Michigan football player quits over concussion concerns, Football
Chris Borland, Fearing for Health, Retires From the 49ers. At 24. - The New York Times
Borland Retirement: Is 24 Too Late to Stop Football Brain Damage?