Is Chris Borland's retirement the beginning of the end for the NFL? (updated) - The Washington Post
NFL rookie Chris Borland on retiring over concussion concerns
49ers' Chris Borland becomes latest young NFL star to retire early - Cincy Jungle
Former Badger retires from NFL fearing head trauma
San Francisco 49ers' Chris Borland retiring from NFL
Former Badgers star Borland surprisingly announces retirement
Chris Borland: Young American football player retires over concerns of brain injuries, The Independent
San Francisco 49ers LB Chris Borland to retire due to safety concerns - Sports Illustrated
Chris Borland retires from 49ers after one year due to fears over head trauma, NFL
49ers Chris Borland retires from football, citing concern over head injuries - Field Gulls
Wary of head trauma, 49ers' Chris Borland retiring at 24